Reload systemd daemon on creation of units location dir in tests.

Systemd manager drops non-existent directories from the units search
path during initialization, thus, creation of UNIT_DIR, if it did not
exist before, requres reloading the daemon.

Signed-off-by: Danila Kiver <danila.kiver@mail.ru>

test/system/250-generate-systemd.bats

@@ -12,7 +12,11 @@ UNIT_FILE="$UNIT_DIR/$SERVICE_NAME.service"
 
 function setup() {
     basic_setup
-    mkdir -p "$UNIT_DIR"
+
+    if [ ! -d "$UNIT_DIR" ]; then
+        mkdir -p "$UNIT_DIR"
+        systemctl --user daemon-reload
+    fi
 }
 
 function teardown() {