sit.glusterfs: Install ansible collections with --no-cache

Recently the following error is seen while trying to install ansible
collections:

[WARNING]: Skipping Galaxy server https://galaxy.ansible.com/api/. Got
  an unexpected error when getting available versions of collection community.general:
  '/api/v3/plugin/ansible/content/published/collections/index/community/general/versions/'
ERROR! Unexpected Exception, this is probably a bug:
  '/api/v3/plugin/ansible/content/published/collections/index/community/general/versions/'

We are already stuck with ansible version from 2.12.x series due to
another issue[1] from gluster-ansible-infra and fix for the above error
is only available from v2.12.8[2]. Given that the fixed version is out
for a while and updates are not yet released via repositories we could
only keep it running with a workaround of disabling the cache while
fetching the versions for a particular collection as described in
upstream issue[3].

[1] gluster/gluster-ansible-infra#135
[2] ansible/ansible#81830 (comment)
[3] ansible/ansible#77911 (comment)

Signed-off-by: Anoop C S <anoopcs@cryptolab.net>

vagrant/roles/sit.glusterfs/tasks/setup/centos.yml

@@ -19,7 +19,7 @@
   block:
     - name: Install ansible collections
       become: no
-      shell: ansible-galaxy collection install {{ item }}
+      shell: ansible-galaxy collection install --no-cache {{ item }}
       loop:
         - ansible.posix
         - community.general