novaclient: Convert v3 boot command with v2.1 spec (security-groups)

The v3 client was written assuming that some arguments
would be renamed for better consistency.   V2.1 will follow
the v2 syntax,  so we need to convert the client back to
that.

This change converts os-security-groups:security-groups to
security-groups in the server element

Change-Id: I50a5b180b7edd645e610ff2d77b6d485924c82a1
Merge "novaclient: Convert v3 boot command with v2.1 spec (security-groups)"