serv.py: Give pr-server up to 5 seconds to commit data

serv.py: Give pr-server up to 5 seconds to commit data

The default value of 0.5 seconds before sending the pr-server a
SIGTERM is not enough to guarantee that sqlite has committed all
the pr data to the database. By polling the pid to see if it is
still running, this allows the pr-server process to shutdown
cleanly and finish the final pr data commit.

Signed-off-by: Konrad Scherer <Konrad.Scherer@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>