Fix issue with concurrent CR creation

The collectd operator is going into deadlock when concurrent update
operations happen within the same controller trying to update the
resource. Fixed this by adding Mutex.

Deleted the old build_image.sh which is replaced by new script which
builds and pushes from inside a builder docker container. This helps in
tackling the dependency issues for image build.

Updated the README for build image script usage.

Issue-ID: ONAPARC-461
Signed-off-by: Dileep Ranganathan <dileep.ranganathan@intel.com>
Change-Id: Ib3c2d1edd266e70bb713885de7ad046ebf5ad086