Fix testGetSettingsContextOnDualDisplayContent flakiness (2)

This is the follow-up CL of [1].

The rare flakiness might happen if we verifying onConfigurationChanged
after placeImeContainer but not comes in time after invocation.

Also, using atLeastOnce might not precide since we don't clear the
previous invocation with Mockito.clearInvications() before the next
verification. Typically, there is only one onConfigurationChanged
happens on both IME container and WindowTokenClient side after
the IME container changed.

To make the test more robost, we can use
verify(..., timeOut(WAIT_TIMEOUT_MS)) with clearng the previous
invocation to improve the above cases.

[1]: Ia915362ff6d81cfb1eb39f426cbf41355c12fa05

Bug: 215874086
Test: Test: atest InputMethodMenuControllerTest#\
   testGetSettingsContextOnDualDisplayContent --rerun-until-failure 100

Change-Id: I50429e09f190bdbea873fc3c0d6128bb44bff321