Remove activity without process before killing from force-stop

Otherwise when killing the process, the died process cannot match
the activities without process, then the process which should be
killed may be started again by resuming the next top activity
while handling visible app died.

Bug: 161334165
Bug: 160236531
Test: atest RootWindowContainerTests#testForceStopPackage
Test: atest CtsAppTestCases:ActivityManagerTest# \
            testForceStopPackageWontRestartProcess
Change-Id: I71b07681f39a8d4e84f5c5c2cd63e064561c3091