network: firewalld: fixed firewall-cmd support

in firewall-cmd 0.3.3 shipped with Fedora 19
firewall-cmd --get-active-zone has changed the output from:
<zone1>: <interface1> <interface2>
to:
<zone1>
  interfaces: <interface1> <interface2>

Dropped _isPermanentSupported: using the version
for detecting --permanent option support

Change-Id: I5fe22c1f05dc98bc71a6ffd6fe28549721cda4f1
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>