cephfs: add a test case for calling Statx on an invalid mount

Adding this test case gets test coverage to 100% for path.go.

Signed-off-by: John Mulligan <jmulligan@redhat.com>

cephfs/path_test.go

@@ -359,6 +359,7 @@ func TestReadlink(t *testing.T) {
 }
 
 func TestStatx(t *testing.T) {
+	t.Run("statPath", func(t *testing.T) {
 		mount := fsConnect(t)
 		defer fsDisconnect(t, mount)
 
@@ -376,6 +377,13 @@ func TestStatx(t *testing.T) {
 		assert.Error(t, err)
 		assert.Nil(t, st)
 		assert.Equal(t, errNoEntry, err)
+	})
+
+	t.Run("invalidMount", func(t *testing.T) {
+		m := &MountInfo{}
+		_, err := m.Statx("junk", StatxBasicStats, 0)
+		assert.Error(t, err)
+	})
 }
 
 func TestRename(t *testing.T) {