Integrate ptf into buildimage (#111)

.gitmodules

@@ -41,3 +41,6 @@
 [submodule "src/sonic-snmpagent"]
 	path = src/sonic-snmpagent
 	url = https://github.com/Azure/sonic-snmpagent
+[submodule "src/ptf"]
+	path = src/ptf
+	url = https://github.com/p4lang/ptf.git

rules/ptf.mk

@@ -0,0 +1,5 @@
+# ptf package
+
+PTF = python-ptf_0.9-1_all.deb
+$(PTF)_SRC_PATH = $(SRC_PATH)/ptf
+SONIC_DPKG_DEBS += $(PTF)

src/ptf

@@ -0,0 +1 @@
+Subproject commit ec33433f027625f4ba85c4eba8258e29f1dd6496