[Thread] do not restart ot-daemon when Thread is disabled

Current implementation will auto-restart ot-daemon even when Thread
has been disabled by ThreadNetworkController#setEnabled(false). This
commit fixes this issue and also adds the "enable" / "disable" shell
command to ease testing.

Bug: 328538612
Change-Id: Icc9360ccf5d7daa6345def75d1860f046600b85b
7 files changed