Refactored the 'os security group list' command to use the SDK
when neutron is enabled, but continue to use the nova client
when nova network is enabled.

This refactor also removes the logic for displaying project names
instead of project IDs when the --all-projects option is specified.
This logic was removed because it is inconsistent with the other
network commands.

Since neutron will always display security groups across all
projects for an admin, the --all-projects option is now hidden
when neutron is enabled and the Project column is always
displayed.

Change-Id: I934a1f5084ef3c5f929d0ffd38ebf5064d799941
Partial-Bug: #1519511
Related-to: blueprint neutron-client

take_action() in commands inheriting from Command returns nothing.
So we should assert the return is None in the unit tests of
these commands.

Change-Id: I953480ecff3b5beb12255d866d0e1df45f130efd
Partial-Bug: #1550636

set/unset comamnd classes should inherit from cliff.Command class.

Change-Id: I54e5608ac0768d7d94b7f7d516ea1948daefdc1b
Partial-Bug: 1546065

Add some test cases that test 'server list' command when specifying flavor or image.
Because I add some attribution to fake.py, I have to change some code
in create server test. Despite all this, I think it's good for testing.

Change-Id: I714deac1f6f940b790a3c20af5f7ffa724ac44d1

Change-Id: I30350076621c83c758927444e5f8bcc2b7d0fc74
Partial-Bug: 1519502
Related-to: blueprint neutron-client

Nothing too complicated here.  I fixed a bunch of spacing issues
that I saw in OSC.

Change-Id: I935ab48e7c5bac5f88ecdb3a05f73fb44fc9f41d