dragonboat: bumped version to v3.2.3

Merge branch 'protobuf-1.4-fix' into release-3.2

dragonboat: bumped version number to v3.2.1

Merge branch 'master' into release-3.2

dragonboat: fixed some missing settings

Merge branch 'inmem_mem_usage_fix' into release-3.1

Merge branch 'rocksdb-log-size-fix' into release-3.1

raft: fixed incorrect observer promotion (lni#94)

dragonboat: fixed a data race when requesting leadership transfer

dragonboat: get ready for the v3.1 release