P2P: Make sure wait for the first client gets stopped
If a group was removed before the wait for the first client had timed
out and the client had not yet connected, p2p_go_wait_client could have
been left set and with that, scan operations could be unnecessarily
delayed. This fixes some undesired delays from commit
c1c0b35fea656345b672984910cc3b93938bc5e5.
Signed-hostap: Jouni Malinen <j@w1.fi>