The test cases discovery_ctrl_char_in_devname and discovery_group_client
tried to allow three P2P_FIND instances to be used before reporting an
error. However, this did not really work properly since the second and
third attempts would likely fail to start the initial special P2P_FIND
scan due to an already ongoing p2p_scan operation. Fix this by stopping
the previous P2P_FIND and waiting for the scan to complete if a retry is
needed.
Signed-off-by: Jouni Malinen <jouni@qca.qualcomm.com>