Add project_sync_gp_distgit to update -patches branches
Add project_sync_gp_distgit to update -patches branches

This function is only useful for the migration to
keep patches up to date. The function reset -patches branch
at the right SHA and re-submit gerrit changes rebased on it.

The cleaning of old gerrit changes must be done manually
by abondonning open/obsolete reviews.

Change-Id: I001e9d937490533bc5199f62e27fc152e362131e

redhat-cip/python-sfrdo