Don't install tempest globally

Devstack installs tempest into a virtualenv with tox when you enable the
tempest service. Because some devs apparently found this confusing it
also installs tempest globally by default.

This global install is redundant and itself makes the jobs longer but
the extra globaly pacakges affect OSC runtime due to pkg_resources
entrypoint iteration. Just remove it since it is unneeded and safe the
time needed to install tempest and iterate its installation on disk.

Change-Id: Ie4375fa82aa745f961e57bee306b695923617b90

devstack-vm-gate.sh

@@ -366,6 +366,13 @@ function setup_localrc {
     # to correctly do testing. Otherwise you are not testing
     # the code you have posted for review.
     localrc_set "$localrc_file" "ERROR_ON_CLONE" "True"
+    # When you enable the tempest service that creates a virtualenv for
+    # tempest. This virtualenv is what we run tests out of. Additionally
+    # devstack installs tempest globally by default. We dont need that
+    # and since the installation process adds to devstack-gate runtime
+    # due to the extra steps and extra packages affecting OSC just don't
+    # install it globally.
+    localrc_set "$localrc_file" "INSTALL_TEMPEST" "False"
     # Since git clone can't be used for novnc in gates, force it to install the packages
     localrc_set "$localrc_file" "NOVNC_FROM_PACKAGE" "True"
     localrc_set "$localrc_file" "ENABLED_SERVICES" "$MY_ENABLED_SERVICES"