Increase max_stacks_per_tenant for tests
Increase max_stacks_per_tenant for tests

Default value for max_stacks_per_tenant is set to 100.
Increase stack count, so we can get higher chances to avoid error in test
when multiple test jobs in progress and hit the limit [1].

[1] http://paste.openstack.org/show/799401/

Change-Id: Ia218563190b61ad646215f0693b533b824e3ed41

openstack/heat,openstack/heat