mon: fix clang error

mon: fix clang error

The specific specialisations in both .h and .cc does not really fly
with Clang

/home/jenkins/workspace/ceph-master/src/mon/MDSMonitor.cc:79:22: error: template parameter redefines default argument
template <int dblV = 7>
                     ^
/home/jenkins/workspace/ceph-master/src/mon/MDSMonitor.h:76:23: note: previous default template argument defined here
  template<int dblV = 7>
                      ^
1 error generated.

Signed-off-by: Willem Jan Withagen <wjw@digiware.nl>