tests: Explicitly close hostapd global control socket on RELOG

tests: Explicitly close hostapd global control socket on RELOG

Without this, the run-tests.py socket could have been left in attached
to receive all hostapd global events during a test case. This could hit
the limit of pending messages on the socket since there is nothing
clearing this socket during the execution of a test case. Fix this by
explicitly closing the socket after having completed the RELOG command.

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