generic/409-411: remove all after unbind mountpoints

After some shared subtrees test (bind/slave/shared/private), maybe
some dentries isn't freed. For example, EBUSY maybe returned due to
some bugs. This patch tries to verify that.

Signed-off-by: Zorro Lang <zlang@redhat.com>
Signed-off-by: Eryu Guan <eguan@redhat.com>

tests/generic/409

@@ -48,6 +48,8 @@ _cleanup()
 	cd /
 	rm -f $tmp.*
 	_clear_mount_stack
+	# make sure there's no bug cause dentry isn't be freed
+	rm -rf $MNTHEAD
 }
 
 # get standard environment, filters and checks
@@ -87,6 +89,7 @@ fs_stress()
 
 # prepare some mountpoint dir
 MNTHEAD=$TEST_DIR/$seq
+rm -rf $MNTHEAD
 mkdir $MNTHEAD 2>>$seqres.full
 mpA=$MNTHEAD/"$$"_mpA
 mpB=$MNTHEAD/"$$"_mpB