Remove Fedora 21 from RPM build as it is EOL

Fedora 21 is EOL'd as of December 1st, 2015.

Announcement:
https://lists.fedoraproject.org/pipermail/announce/2015-November/003296.html

Fedora 21 will reach end of life on 2015-12-01, and no further updates
will be pushed out after that time. Additionally, with the recent
release of Fedora 23, no new packages will be added to the Fedora 21
collection.

Please see https://fedoraproject.org/wiki/DNF_system_upgrade for more
information on upgrading from Fedora 21 to a newer release.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

contrib/builder/rpm/fedora-21/Dockerfile

@@ -1,37 +0,0 @@
-#
-# THIS FILE IS AUTOGENERATED; SEE "contrib/builder/rpm/generate.sh"!
-#
-
-FROM fedora:21
-
-RUN yum install -y @development-tools fedora-packager
-RUN yum install -y btrfs-progs-devel device-mapper-devel glibc-static libseccomp-devel libselinux-devel libtool-ltdl-devel selinux-policy selinux-policy-devel sqlite-devel tar
-
-ENV SECCOMP_VERSION v2.2.3
-RUN buildDeps=' \
-automake \
-libtool \
-' \
-&& set -x \
-&& yum install -y $buildDeps \
-&& export SECCOMP_PATH=$(mktemp -d) \
-&& git clone -b "$SECCOMP_VERSION" --depth 1 https://github.com/seccomp/libseccomp.git "$SECCOMP_PATH" \
-&& ( \
-cd "$SECCOMP_PATH" \
-&& ./autogen.sh \
-&& ./configure --prefix=/usr \
-&& make \
-&& install -c src/.libs/libseccomp.a /usr/lib/libseccomp.a \
-&& chmod 644 /usr/lib/libseccomp.a \
-&& ranlib /usr/lib/libseccomp.a \
-&& ldconfig -n /usr/lib \
-) \
-&& rm -rf "$SECCOMP_PATH"
-
-ENV GO_VERSION 1.5.2
-RUN curl -fSL "https://storage.googleapis.com/golang/go${GO_VERSION}.linux-amd64.tar.gz" | tar xzC /usr/local
-ENV PATH $PATH:/usr/local/go/bin
-
-ENV AUTO_GOPATH 1
-
-ENV DOCKER_BUILDTAGS seccomp selinux

contrib/builder/rpm/generate.sh

@@ -5,7 +5,7 @@ set -e
 #    ie: ./generate.sh
 #        to update all Dockerfiles in this directory
 #    or: ./generate.sh
-#        to only update fedora-20/Dockerfile
+#        to only update fedora-23/Dockerfile
 #    or: ./generate.sh fedora-newversion
 #        to create a new folder and a Dockerfile within it
 
@@ -22,7 +22,7 @@ for version in "${versions[@]}"; do
 	suite="${version##*-}"
 	from="${distro}:${suite}"
 	installer=yum
-	if [[ "$distro" == "fedora" ]] && [[ "$suite" -ge "22" ]]; then
+	if [[ "$distro" == "fedora" ]]; then
 		installer=dnf
 	fi
 

docs/installation/fedora.md

@@ -11,7 +11,7 @@ weight=-3
 
 # Fedora
 
-Docker is supported Fedora version 21 and 22. This page instructs you to install
+Docker is supported on Fedora version 22 and 23. This page instructs you to install
 using Docker-managed release packages and installation mechanisms. Using these
 packages ensures you get the latest release of Docker. If you wish to install
 using Fedora-managed packages, consult your Fedora release documentation for

hack/make/release-rpm

@@ -7,9 +7,9 @@ set -e
 # 	http://yum.dockerproject.org/repo/$release/$distro/$distro-version
 #
 # For example:
-# 	http://yum.dockerproject.org/repo/main/fedora/22
-# 	http://yum.dockerproject.org/repo/testing/centos/6
-# 	http://yum.dockerproject.org/repo/experimental/fedora/21
+# 	http://yum.dockerproject.org/repo/main/fedora/23
+# 	http://yum.dockerproject.org/repo/testing/centos/7
+# 	http://yum.dockerproject.org/repo/experimental/fedora/23
 # 	http://yum.dockerproject.org/repo/main/centos/7
 #
 # ... and so on and so forth for the builds created by hack/make/build-rpm

project/ISSUE-TRIAGE.md

@@ -18,7 +18,7 @@ Before triaging an issue very far, make sure that the issue's author provided th
 -   the output of `docker info`
 -   the output of `uname -a`
 -   a reproducible case if this is a bug, Dockerfiles FTW
--   host distribution and version ( ubuntu 14.04, RHEL, fedora 21 )
+-   host distribution and version ( ubuntu 14.04, RHEL, fedora 23 )
 -   page URL if this is a docs issue or the name of a man page 
 
 Depending on the issue, you might not feel all this information is needed. Use your best judgement.  If you cannot triage an issue using what its author provided, explain kindly to the author that they must provide the above information to clarify the problem.