ceph_authtool.cc: use empty() instead of size()

Use empty() since it should be prefered as it has, following the
standard, a constant time complexity regardless of the containter
type. The same is not guaranteed for size().

warning from cppchecker was:
[src/ceph_authtool.cc:124]: (performance) Possible inefficient
  checking for 'caps' emptiness.
[src/ceph_authtool.cc:237]: (performance) Possible inefficient
  checking for 'caps' emptiness.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
mds/CDentry.h: use projected.empty() instead of projected.size()

Use empty() since it should be prefered as it has, following the
standard, a constant time complexity regardless of the containter
type. The same is not guaranteed for size().

warning from cppchecker was:
[src/mds/CDentry.h:234]: (performance) Possible inefficient
  checking for 'projected' emptiness.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
mds/MDSMap.h: use up.empty() instead of up.size()

Use empty() since it should be prefered as it has, following the
standard, a constant time complexity regardless of the containter
type. The same is not guaranteed for size().

warning from cppchecker was:
[src/mds/MDSMap.h:448]: (performance) Possible inefficient
  checking for 'up' emptiness.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
client/Client.cc: use empty() instead of size()

Use empty() since it should be prefered as it has, following the
standard, a constant time complexity regardless of the containter
type. The same is not guaranteed for size().

warning from cppchecker was:
[src/client/Client.cc:3649]: (performance) Possible inefficient
  checking for 'mds_sessions' emptiness.
[src/client/Client.cc:7489]: (performance) Possible inefficient
  checking for 'osds' emptiness.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
src/client/SyntheticClient.cc: use !subdirs.empty() instead of size()

Use empty() since it should be prefered as it has, following the
standard, a constant time complexity regardless of the containter
type. The same is not guaranteed for size().

warning from cppchecker was:
[src/client/SyntheticClient.cc:2706]: (performance) Possible
  inefficient checking for 'subdirs' emptiness

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
cls/lock/cls_lock.cc: use !lockers.empty() instead of size()

Use empty() since it should be prefered as it has, following the
standard, a constant time complexity regardless of the containter
type. The same is not guaranteed for size().

warning from cppchecker was:
[src/cls/lock/cls_lock.cc:209]: (performance) Possible inefficient
  checking for 'lockers' emptiness.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
Merge pull request #62 from dalgaaf/wip-da-sca-cppcheck-performance-3

More performance patches 

Reviewed-by: Sage Weil <sage@inktank.com>