[Manila] Fix grenade job settings
[Manila] Fix grenade job settings

Manila uses plugin mechanism for enabling devstack and grenade plugins.
Design of grenade plugin assumes that it enables devstack plugin
using specific versions via its config. But now, CI job enables master
version of devstack plugin. It leads to duplication, manila installation
runs twice and, therefore, fails.
Remove redundant string from grenade job configuration for Manila
project avoiding this duplication.

Also, remove 'DEVSTACK_GATE_TEMPEST=1' env var from job config as
manila's case does not require it. It triggers run of redundant
tests. But enable tempest via "ENABLED_SERVICES" to be able to
trigger tempest run in manila grenade scripts not depending on
'devstack-gate' project scripts in future.

Change-Id: Ib5b7df457101430813db89320dcc3d3f8438f252

openstack-infra/project-config,Tesora/tesora-project-config,dongwenjuan/project-config,openstack-infra/project-config,dongwenjuan/project-config,Tesora/tesora-project-config