D-Bus Fix network_is_persistent_group() for P2P operations

D-Bus Fix network_is_persistent_group() for P2P operations

Commit c2762e410fa319f75a174aeb12343beddf99fce4 ('P2P: Update D-Bus
network object semantics during group formation') added this helper
function to determine whether a network block is used for storing a
persistent group information. However, it implemented this in a way that
matches both persistent group storage and an operating persist group
instance. This does not seem to match the expected behavior for the
D-Bus objects, so fix this to match only the persistent group storage
case to avoid registering/unregistered incorrect D-Bus objects for
groups.

Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>