Fix memory leak

Fixes

Indirect leak of 1296 byte(s) in 6 object(s) allocated from:
    #0 0x7f27984ffda8 in operator new(unsigned long) /afs/cern.ch/cms/CAF/CMSCOMM/COMM_ECAL/dkonst/GCC/build/contrib/gcc-8.2.0/src/gcc/8.2.0/libsanitizer/lsan/lsan_interceptors.cc:229
    #1 0x7f279215ff95 in ANNSvc::ANNSvc(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, ISvcLocator*, std::vector<Gaudi::StringKey, std::allocator<Gaudi::StringKey> > const&) Hlt/HltServices/src/ANNSvc.cpp:119