Create and delete flavor as regular user

The new negative test cases are trying to perform compute admin
 operations as regular user.
Regular user should not be able to create or delete flavor.

Change-Id: Icec59ba9e39b8a9c9ea93e5e633989c962f42e33
Remove unused variables

test_server_rescue.py: client assigned, but never read in
			test_rescued_vm_attach_volume.
test_attach_volume.py: "attached" member used without the "self."

Change-Id: I2c3942ee9fde7cd92144ac879aaff99f136cab7f
Add missing exceptions import

security_groups_client.py and security_groups_client.py are using the
"exceptions" module, but it was not imported.

Change-Id: Ib39e28ad7a4a49833ac9a4090da5b783e3075a03
Merge "Remove unused variables"
Merge "Add missing exceptions import"
Merge "Create and delete flavor as regular user"