This change implements the change to allow testr to run in serial which
should resolve most issues with tempest on a resource constrained host.
The problem that is being resolved here is that testr will, by default,
run in multi-threaded and has a relitively high probability to result in
a 503. This primarily impacts the gate jobs as they are built on a hosts
with 4 CPUs and 8GB of ram.
By default if the tempest script is run, testr will run multi-threaded.
However, if the environment variable RUN_TEMPEST_OPTS is set to
'--serial' then it will run in serial. This is done for the
gate-check-commit script so that the change only affects the AIO gate
check.
An additional environment variable TESTR_OPTS is added for further
flexibility.
Co-Authored-By: Jesse Pretorius <jesse.pretorius@rackspace.co.uk>
Closes-Bug: #1428847
Change-Id: I8c7ac72ef46ae3f3af3d3503081bec0cbe7276e9
255b94d425