'policy' should be required in server_group_create

The 'policies' param is a required param in nova api now.
So, we also need to change it in cli.

After the modification, the 'policy' param will be required now,
and the old '--policy' style will still be available.

Change-Id: I97921eef0f635c8d50a04bbdaf3ef4f1bfaa3e9d
Closes-Bug: #1323909
"nova boot" should not log an error if subsidiary commands fail

Fix:
Intially the cli was raising "CommadError" in case the requested
flavor or image were not present.
This error category was not approrpiate as it signifies an error
in the command syntax. When the requested resource (flavour/image)
does not exist, a ResourceNotFound error should be raised. So,
added a new error category "ResourceNotFound" to cater for this
scenario and updated the code to raise this new error.
"nova show <instance_name>" command has also been updated to raise
"ResourceNotFound" error when the requested vm for which details
have to be displayed does not exist.

Closes-Bug: #1258488
Change-Id: If64a087944586ef5792efe3baa62e455b9bbaa07
Look for all accessible flavors by default, not just public ones

The Nova server will restrict unprivileged user accounts to just
public images, while allowing administrator accounts access to
all. The Nova client shouldn't force the flavor name lookup to
be restricted to just public images, since that breaks the ability
to the flavor name when booting an instance

Fixes bug #1327212

Change-Id: I949aec52660242249b8cba51d77bfdc1acaf31d2
Merge ""nova boot" should not log an error if subsidiary commands fail"
Merge "Look for all accessible flavors by default, not just public ones"
add disk bus and device type to volume attach

This change adds the optional parameters: disk bus and device type
to the volume-attach command for the V3 API.

DocImpact
Closes-Bug: #1303875

Change-Id: I4fd07726887d08e5b669139b559bdb2c2d21826e
Merge "'policy' should be required in server_group_create"