Make existing requirements parsing more forgiving

* jenkins/scripts/project-requirements-change.py: If not reading
requirements in strict mode, for example when analyzing the existing
branch tip copy of a list, allow for the possibility that
pkg_resources may be incapable of parsing what it sees as a
malformed version string.

Change-Id: I8e13a5e94901f615233ddfb4a5e4589841a01853
Merge "Make existing requirements parsing more forgiving"