tests: Change list_networks() to use global interface with P2P

tests: Change list_networks() to use global interface with P2P

list_networks() always used the wlanX control interface to query for the
current list of networks. However, when a dedicated P2P Device is used,
the global control interface should be used when checking persistent
group network profiles.

Fix this by adding an optional parameter indicating that the P2P
networks are requested, and in such a case use the global control
interface.

In addition update test_p2p_persistent to use the argument when needed.

Signed-off-by: Ben Rosenfeld <ben.rosenfeld@intel.com>