Don't overwrite TERM in containers (#2027)

Don't overwrite $TERM env-var in container images, the terminal (provided by dockerd or whatever) will set it correctly. the current setting causes issues in e.g. vim where some operations (like ctrl+left/ctrl+right) completely butcher the file being edited.

toolkit/imageconfigs/core-container.json

@@ -17,9 +17,9 @@
             ],
             "PostInstallScripts": [
                 {
-                    "Path": "postinstallscripts/core-container/cleanup-and-set-term.sh"
+                    "Path": "postinstallscripts/core-container/cleanup.sh"
                 }
             ]
         }
     ]
-}
+}

toolkit/imageconfigs/postinstallscripts/core-container/cleanup.sh

@@ -4,5 +4,3 @@ rm -rf /boot/*
 rm -rf /usr/src/
 rm -rf /home/*
 rm -rf /var/log/*
-# set TERM to linux
-echo "export TERM=linux" >> /etc/bash.bashrc