Fixes "bad format" in replicator for valid hosts

Due to a bad regex, the glance-replicator tool rejects any source or
target host:port combination that contains a period. As a result, only
hostnames without periods can be used.

This fix expands the host/port checks to:
  - allow periods in hostnames
  - allow and verify IPv6 addr/port pairs (i.e., [fe80::f00d:face]:1234)
  - allow and verify IPv4 addr/port pairs (i.e., 172.17.17.2:1234)
  - sanity-check port numbers

This also includes extensive tests for each component of the parsing,
and adds network_utils to openstack-common.conf.

Change-Id: I94fdd7a57a4cb0aa5d79f66d68be159d1f1266d1
Closes-Bug: #1216247
Merge "Fixes "bad format" in replicator for valid hosts"