tests: Move P2P-REMOVE-AND-REFORM-GROUP cases more robust

tests: Move P2P-REMOVE-AND-REFORM-GROUP cases more robust

Wait for the AP-DISABLED and AP-ENABLED group events before reading the
current group operation frequency after P2P-REMOVE-AND-REFORM-GROUP.
This reduces a possibility of a race condition making a test case fail
with the returned frequency being 0 when reading this before the
reformed group is fully up. This may help avoid false error reports for
the following test cases: p2p_go_move_reg_change p2p_go_move_scm
p2p_go_move_scm_peer_supports p2p_go_move_scm_multi.

Signed-off-by: Jouni Malinen <j@w1.fi>