tests: Make it less likely to overflow wlan5 control iface socket

tests: Make it less likely to overflow wlan5 control iface socket

Number of test cases did not read all control interface socket events
from the dynamically added wlan5 interface. This could result in hitting
maximum socket TX queue length and failures in the following test cases.

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