libmount: remove support for deleted mount table entries

The "(deleted)" suffix has been originally used by kernel for deleted
mountpoints. Since kernel commit 9d4d65748a5ca26ea8650e50ba521295549bf4e3
(Dec 2014) kernel does not use this suffix for mount stuff in /proc at
all. Let's remove this support from libmount too.

Signed-off-by: Karel Zak <kzak@redhat.com>