Add a unit test for the Gluster storage type
Add a unit test for the Gluster storage type

This patch, extends the 'ganeti.utils.storage_unittest.py' unit test
with a new test for the Gluster storage type. Also, the current unit
tests are updated accordingly to correspond to the latest changes.

Signed-off-by: Dimitris Bliablias <56dc08131759a716534a4a0da56f0029eaf4af5d@gmail.com>
Signed-off-by: Petr Pudlak <9d19625f8ee825a2c398462ed335cbcf98f79c32@google.com>
Reviewed-by: Petr Pudlak <9d19625f8ee825a2c398462ed335cbcf98f79c32@google.com>

mbakke/ganeti,apyrgio/ganeti,dimara/ganeti,bitemyapp/ganeti,ganeti-github-testing/ganeti-test-1,yiannist/ganeti,andir/ganeti,leshchevds/ganeti,grnet/snf-ganeti,dimara/ganeti,ganeti/ganeti,ganeti/ganeti,leshchevds/ganeti,ganeti/ganeti,bitemyapp/ganeti,onponomarev/ganeti,yiannist/ganeti,leshchevds/ganeti,onponomarev/ganeti,andir/ganeti,mbakke/ganeti,grnet/snf-ganeti,yiannist/ganeti,ganeti-github-testing/ganeti-test-1,mbakke/ganeti,andir/ganeti,apyrgio/ganeti