Allow mozilla to send dbus messages to gconfd

Firefox throws the following error when it starts if it cannot talk to gconfd

Configuration server couldn't be contacted: D-BUS error: An SELinux
policy prevents this sender from sending this message to this recipient,
0 matched rules; type="method_call", sender=":1.120" (uid=1000 pid=26773
comm="/opt/firefox/firefox ") interface="org.gnome.GConf.Server"
member="GetDefaultDatabase" error name="(unset)" requested_reply="0"
destination="org.gnome.GConf" (uid=1000 pid=20128
comm="/usr/libexec/gconfd-2 ")

Signed-off-by: Jason Zaman <jason@perfinion.com>