Do not write error if bitcoind process not found

We unconditionally kill `bitcoind` in the integration test script. This
is correct but when there is no `bitcoind` process running results in a
output `bitcoind: no process found`. This output is misleading because
it makes one think that `bitcoind` didn't start up correctly.

Send the stderr warning to `/dev/null`.

Author: tcharding

integration_test/run.sh

@@ -7,7 +7,7 @@ rm -rf ${TESTDIR}
 mkdir -p ${TESTDIR}/1
 
 # To kill any remaining open bitcoind.
-killall -9 bitcoind
+killall -9 bitcoind 2> /dev/null
 
 echo $PATH