b/7378607: more tweaks to reduce jank interacting with the keyboard.
b/7378607: more tweaks to reduce jank interacting with the keyboard.

- remove the hack to hide keyboard in activity onPause(). Yay!
- hide the compose panel in onRestart(), so it doesn't flash when
we re-enter the activity thru. onRestart(). Show the compose panel
later when we load messages+draft.

Change-Id: I314e9298b7b4cfc54a4407d2521b70473d70ee30

bmaupin/android-sms-plus