test_cls_version.cc: don't free object twice, free the right one

Object 'librados::ObjectWriteOperation *op' is freed twice in the TEST
test_version_inc_read. Free instead 'librados::ObjectReadOperation *rop'

Related cppcheck warning:
 [src/test/cls_version/test_cls_version.cc:79]: (error) Memory
  pointed to by 'op' is freed twice.

This should also fix:

CID 1049247 (#1 of 1): Use after free (USE_AFTER_FREE)
  deref_arg: Calling "librados::ObjectWriteOperation::~ObjectWriteOperation()"
  dereferences freed pointer "op". (The dereference happens because this is
  a virtual function call.)
CID 1049218 (#4 of 4): Resource leak (RESOURCE_LEAK)
  leaked_storage: Variable "rop" going out of scope leaks the storage it
  points to.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
rgw/rgw_bucket.cc: use static_cast<>() instead of C-Style cast

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
mon/PGMonitor.cc: reduce scope of local 'num_slow_osds' variable

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