[ARCHIVES] Do not set the branch for archived repositories

[ARCHIVES] Do not set the branch for archived repositories

setting istanbul for all the repo triggered a regression
in fact some archived repositories have no istanbul branch
an ARCHIVED_ONAP_TAG set to master has been introduced
so it does not require to create new branch for archived repositories
(not possible as the repo is in readonly)
another option would be to set directly the last sha1 for the 2
repositories delaing with this issue
- heatbridge
- python-test-utils

Issue-ID: INT-2044

Signed-off-by: morganrol <morgan.richomme@orange.com>
Change-Id: Iff72ca4625d7be7b9e805c58096ce8d5b62118b6