tests: zabbix: Set 'PATH' before running the scripts.

This is a followup to 8b9cad01e9.

* gnu/tests/monitoring.scm (run-zabbix-server-test)[test]: Set 'PATH' in
MARIONETTE.

gnu/tests/monitoring.scm

@@ -194,6 +194,13 @@ cat ~a | sudo -u zabbix psql zabbix;
                 (start-service 'postgres))
              marionette))
 
+          ;; Add /run/setuid-programs to $PATH so that the scripts passed to
+          ;; 'system' can find 'sudo'.
+          (marionette-eval
+           '(setenv "PATH"
+                    "/run/setuid-programs:/run/current-system/profile/bin")
+           marionette)
+
           (test-eq "postgres create zabbix user"
             0
             (marionette-eval '(begin (system #$%psql-user-create-zabbix))