Take new cpp-common and libmemcached to fix https://github.com/Metaswitch/cpp-common/issues/9 and https://github.com/Metaswitch/cpp-common/issues/8
Merge pull request #361 from Metaswitch/updated-submodules

[No review required] Take new cpp-common and libmemcached to fix https://github.com/Metaswitc...