mnt_entry contains a few strings and they should be release too

CID 996198 (#4 of 4): Resource leak (RESOURCE_LEAK)
20. leaked_storage: Variable "pm" going out of scope leaks the storage
it points to.

CID 996190 (#1 of 1): Resource leak (RESOURCE_LEAK)
13. leaked_storage: Variable "new" going out of scope leaks the storage
it points to.
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>