Fix delayed hide soft input when switch user

The user switch task may cost some time and delay
to send the hide soft input action. It likely happended
when system is busy(e.g. starting winscope trace).

1. Try to fix this by sending the hide soft input action
   before user switch task.
2. Remove the mSystemReady checking since user switch task
   should be always posted afterward.

Bug: 176291101
Test: atest CtsInputMethodTestCases
Change-Id: I1689e7a7a30ed717520e9d3c160e1727202ee15b