The standard IPv4 loopback address is 127.0.0.1, however anything in
the 127.0.0.0/8 range is also a loopback address.
isLoopback returns true for any address that is in the IPv4 loopback
address range, or is the single IPv6 loopback address ::1
Task-number: QTBUG-22246
Change-Id: Ic39100e2e97a52db700e01b109998a1cfd4335e3
Reviewed-by: Thiago Macieira (Intel) <thiago.macieira@intel.com>