[ROBOT] Set version to 1.7.3

[ROBOT] Set version to 1.7.3

due to the reinsourcing of the chart in OOM, I missed
the guilin maintenance update from 1.7.2 to 1.7.3
There are ongoing discussions on the future of this pod
It is not really used by the integration team
but it may still be used by operation teams
a mail has been sent to get a broader view on who is using
this pod, references in use case documentation are also
under investigation

This pod shall be either remove or heaviliy refactored to follow the
rules than the other ONAP components (no root, limits, no full distri
no python 2.7, micro service approach,...) and it shall be launch out
of onap namespaces (onap-testing)

Meanwhile the master version shall be at least aligned with
the guilin version..

Issue-ID: TEST-283

Signed-off-by: morganrol <morgan.richomme@orange.com>
Change-Id: I2709c6fa5046ad7f72ee86a75269dd4672386a3c