[Service] Refactor stop service sequence

[Service] Refactor stop service sequence

When service application needs to terminate by tizen://exit, it
should call wrt.stopService(id).

However, it is called in worker thread with standalone model,
WRTServiceManager::Remove() will be handled in worker thread, not
main thread. then, uv loop sometimes makes abort() or get SIGSEGV.
Then, wrt.stopService(id) should be called in main thread side.

Change-Id: I103bf8f38111db984bb22d0af56c05456851b681
Signed-off-by: DongHyun Song <dh81.song@samsung.com>