test_rgw_admin_meta.cc: prefer ++operators for iterators

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
test_rgw_admin_opstate.cc: prefer ++operators for iterators

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
test_rgw_admin_log.cc: prefer empty() over size() for emptiness check

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
test_cls_rbd.cc: use 'delete []' if 'new char[len]' was used

Fix for:
[src/test/cls_rbd/test_cls_rbd.cc:82]: (error) Mismatching allocation
 and deallocation: b
[src/test/cls_rbd/test_cls_rbd.cc:95]: (error) Mismatching allocation
 and deallocation: b
[src/test/cls_rbd/test_cls_rbd.cc:97]: (error) Mismatching allocation
 and deallocation: b

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
test_rgw_admin_log.cc: prefer ++operators for iterators

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
rgw_quota.cc: remove unused variable 'key'

[src/rgw/rgw_quota.cc:455]: (style) Variable 'key' is assigned a
 value that is never used.

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
rgw_op.cc: use static_cast instead of c-style cast

Signed-off-by: Danny Al-Gaaf <danny.al-gaaf@bisect.de>
rgw_op.cc: reduce scope of 'int r' in execute()

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