tests: Be more careful in clearing REGDOM state

tests: Be more careful in clearing REGDOM state

cfg80211 regulatory code gets into pretty inconvenient state if it needs
to intersect regulatory domain information from multiple regulations
(country=98). The existing mechanisms in the hwsim test cases are not
able to clear that up for the following test case and this can result in
large number of failures.

It looks like country=98 case is hit frequently in WNM test cases where
a station associates with an AP that advertises a specific country code
and that station is then asked to disconnect before the REGDOM events
have been received. Avoid this by waiting for the REGDOM events for the
init=COUNTRY_IE case before disconnecting.

Signed-off-by: Jouni Malinen <jouni@codeaurora.org>