test: Cleanup volume group in one non-destructive test

Just janking out the disk will leave debris behind in /dev.

test/verify/check-storage-mounting

@@ -432,6 +432,7 @@ class TestStorageMountingLUKS(storagelib.StorageCase):
         disk = self.add_ram_disk()
         b.wait_in_text("#drives", disk)
         m.execute(f"vgcreate test {disk}; lvcreate test -n one -L 20M; lvcreate test -n two -L 20M")
+        self.addCleanup(m.execute, "vgremove --force test 2>/dev/null || true")
         b.click('#devices .sidepanel-row:contains("test")')
         b.wait_visible("#storage-detail")
         self.content_row_wait_in_col(1, 1, "one")