packaging: services: prepend pythonlib

devenv should shadow default search path, so system library will not
shadow devenv.

Related-To: https://bugzilla.redhat.com/show_bug.cgi?id=1009863
Change-Id: I5383c6529e822d92593d2e915a76bc3b25855866
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>