mds/MDSDaemon.cc: fix resource leak in MDSDaemon

mds/MDSDaemon.cc: fix resource leak in MDSDaemon

Delete mdsmap in descructor. Remove not needed checks for
mds_rank and objecter before call delete since the C++ standard
allows the deletion of pointer with NULL-value. The check is
redundant.

Fix for:
CID 1316224 (#1 of 1): Resource leak in object (CTOR_DTOR_LEAK)
1. alloc_new: Allocating memory by calling new MDSMap.
2. var_assign: Assigning: this->mdsmap = new MDSMap.
3. ctor_dtor_leak: The constructor allocates field mdsmap of MDSDaemon
   but the destructor and whatever functions it calls do not free it.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>