Optionally skip tag during release process

Optionally skip tag during release process

Make tag process optional. True by default.

Example scenario:
Some ONAP projects make both maven and docker releases
for a single repo. Docker releases depend on maven releases.
This means that the team needs to make a maven release first,
then make a docker release and lastly, tag the repo.

This change will allow them to hold the tagging part during
maven releases to allow them to tag after the docker release is made.

Issue: RELENG-2835
Signed-off-by: Jessica Wagantall <jwagantall@linuxfoundation.org>
Change-Id: Ibd206269b80e7fb788682a81e038aa74d9eaf97c