When screen-reader e.g. crashed, bus-launcher didn't check if the process
is still running before it tried to terminated it. In result screen-reader's
invalid PID was kept and new screen-reader couldn't be launched.
Change-Id: I599c7e7962a16b031e913c1a957b2f33f225a6f3 Signed-off-by: Tomasz Olszak <t.olszak@samsung.com>