Allow kwargs in create_timestamp

As a part of the scenario/manager.py stabilization tracked by
the below BP the patch adds kwargs argument for create_timestamp
method so that the consumers are able to pass additional
parameters if needed.

Change-Id: I2d204d98c5e22c89e6b44514c29b74b55e2456d2
Implements: blueprint tempest-scenario-manager-stable
1 file changed