Fix stealthy problem with std::lock_guard use in BCFKeyValueData::import_gvcf
Fix stealthy problem with std::lock_guard use in BCFKeyValueData::import_gvcf

http://stackoverflow.com/q/25059787

Wow, what a nasty dark corner of C++. cc @orodeh @yifei-men

dnanexus-rnd/GLnexus,dnanexus-rnd/GLnexus,dnanexus-rnd/GLnexus