fixes #767 correct allocation issue in native maps (#769)
fixes #767 correct allocation issue in native maps (#769)

This fixes a bug that was found when building the native maps against
Fedora 29.  The cause of the bug was that an empty C++ map seemed to
allocate a small amount of memory, which was a new behavior.  This new
behavior violated an assumption made by the custom alloctor used by the
native map code.  The code was restructured to avoid this issue.
milleruntime/accumulo,lstav/accumulo,lstav/accumulo,ctubbsii/accumulo,phrocker/accumulo-1,ivakegg/accumulo,apache/accumulo,apache/accumulo,ctubbsii/accumulo,phrocker/accumulo-1,lstav/accumulo,ivakegg/accumulo,apache/accumulo,keith-turner/accumulo,ivakegg/accumulo,ctubbsii/accumulo,milleruntime/accumulo,milleruntime/accumulo,keith-turner/accumulo,ctubbsii/accumulo,keith-turner/accumulo,lstav/accumulo,mjwall/accumulo,mjwall/accumulo,milleruntime/accumulo,ctubbsii/accumulo,milleruntime/accumulo,lstav/accumulo,apache/accumulo,apache/accumulo,ctubbsii/accumulo,ivakegg/accumulo,mjwall/accumulo,ctubbsii/accumulo,phrocker/accumulo-1,ivakegg/accumulo,phrocker/accumulo-1,apache/accumulo,phrocker/accumulo-1,ivakegg/accumulo,ivakegg/accumulo,milleruntime/accumulo,keith-turner/accumulo,phrocker/accumulo-1,lstav/accumulo,keith-turner/accumulo,keith-turner/accumulo,milleruntime/accumulo,phrocker/accumulo-1,keith-turner/accumulo,lstav/accumulo,mjwall/accumulo,mjwall/accumulo,apache/accumulo,mjwall/accumulo,mjwall/accumulo