Fix install in the presence of old modules

If older incompatible version of osmopython is already available, it
might be chosen fori mport instead of current version. Fix this by
explicitly prepending the proper version to path.

Change-Id: Icbe2af1e3815406213be29e0c0360432dc9fd6fb
Related: OS#2821

tests/test_py3.py

@@ -7,7 +7,7 @@ import asyncio, random, sys, os
 # we have to use this ugly hack to workaroundbrokenrelative imports in py3:
 # from ..osmopy.osmo_ipa import Ctrl
 # does not work as expected
-sys.path.append(os.path.dirname(os.path.dirname(os.path.realpath(__file__))))
+sys.path.insert(0, os.path.dirname(os.path.dirname(os.path.realpath(__file__))))
 from osmopy.osmo_ipa import Ctrl
 from osmopy import __version__