Add ryu team to the MAINTAINERS file for ofagent and ryu

Change-Id: I02fa641c34248c9e6bbaab5caa66892165308c36
Test against latest glance_store code

Install glance_store from git so we can test Glance against master. This
is useful for both, glance and glance_store gates, to make sure nothing
is broken there.

Change-Id: I6c01165c4384c41f46f2c32d64475703b3178dab
Increase CEPH_LOOPBACK_DISK_SIZE_DEFAULT to 4GB

CEPH_LOOPBACK_DISK_SIZE_DEFAULT should be more than 2GB
to make volume snapshot feature works. 2GB is not enough
because min Cinder volume size is 1GB and no snapshot
could be created.

This also fixes related Tempest tests and experimental
check-tempest-dsvm-full-ceph gate job.

Change-Id: Ifa41d0d1764d68ea02dcb32a5fc62f7f6282904d
Merge "Test against latest glance_store code"
Merge "Add ryu team to the MAINTAINERS file for ofagent and ryu"
Merge "Increase CEPH_LOOPBACK_DISK_SIZE_DEFAULT to 4GB"
Merge branch 'master' of https://github.com/openstack-dev/devstack