Quote a variable in zz_evobackup.default.sh.j2

This allows us to remove the shellcheck ignore warning comment and puts it in line with upstream. Apparently, the file can only contain one PID, so it's okay to quote the variable.

evobackup-client/templates/zzz_evobackup.default.sh.j2

@@ -124,9 +124,7 @@ pick_server() {
 if [ -e "${PIDFILE}" ]; then
     pid=$(cat "${PIDFILE}")
     # Does process still exist ?
-    # ignore check because multiple processes might exist
-    # shellcheck disable=SC2086
-    if kill -0 ${pid} 2> /dev/null; then
+    if kill -0 "${pid}" 2> /dev/null; then
         # Killing the childs of evobackup.
         for ppid in $(pgrep -P "${pid}"); do
             kill -9 "${ppid}";