Separate security_group_rules_client

As the qa-spec of consistent-service-method-names, we have decided
all service client modules will be separated into a single module
by each resource. So this patch separates security_group_rules_client
from security_groups_client.

Partially implements blueprint consistent-service-method-names

Change-Id: I28fab7730f62606c771631faf94203dbdd517358
11 files changed