tests: kill all started processes on exit

Just killing MongoDB is not enough, we also need to kill processes such
as the cat ones used to read the fifo.

Change-Id: I3fd99e333e69625e3872e24b9337cad17d46d737

run-tests.sh

@@ -4,9 +4,7 @@ set -e
 function clean_exit(){
     local error_code="$?"
     rm -rf ${MONGO_DATA}
-    if [ "$MONGO_PID" ]; then
-        kill -9 ${MONGO_PID} || true
-    fi
+    kill $(jobs -p)
     return $error_code
 }
 
@@ -33,7 +31,6 @@ then
     exit 1
 fi
 mongod --maxConns 32 --nojournal --noprealloc --smallfiles --quiet --noauth --port ${MONGO_PORT} --dbpath "${MONGO_DATA}" --bind_ip localhost --config /dev/null &>${MONGO_DATA}/out &
-MONGO_PID=$!
 # Wait for Mongo to start listening to connections
 while read line
 do