Produce vpp_papi*.egg for virtual environments

Produce vpp_papi*.egg so that virtual environments (e.g. virtualenv)
could install vpp_papi inside them.

Change-Id: I9664d119a64f4968de44a7a430aec4879ed02b16
Signed-off-by: Igor Mikhailov (imichail) <imichail@cisco.com>
diff --git a/src/vpp-api/python/Makefile.am b/src/vpp-api/python/Makefile.am
index 6f5beb6..be73d28 100644
--- a/src/vpp-api/python/Makefile.am
+++ b/src/vpp-api/python/Makefile.am
@@ -18,4 +18,5 @@
 	--root /                                                        \
 	--prefix $(DESTDIR)$(prefix)                                    \
 	--single-version-externally-managed                             \
-	--verbose)
+	--verbose                                                       \
+	bdist_egg)