tests: Make nfc_wps more robust by avoiding race conditions

tests: Make nfc_wps more robust by avoiding race conditions

The hostapd side operations and data connectivity test were executed
without explicitly waiting for hostapd to report connection as having
been completed. This could result in trying to transmit data before
EAPOL-Key msg 4/4 was processed especially when using UML time-travel.
Make this more robust by waiting for hostapd to be ready before the data
test.

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