Reset top activity's mWaitForEnteringPinnedMode when aborting an incomplete pip-entry

When aborting an incomplete pip-entry, reset top activity mWaitForEnteringPinnedMode to prevent skipping it's window frame computation later.

Bug: 318553345
Test: Manual test

Change-Id: I9378f54957534c2fab7d877d03bd40d2573959da
Signed-off-by: buwenjing <buwenjing@xiaomi.com>