Fix for bug 1373179

Native Hbase Table access via Trafodion dumps core.
The error messages passed from Java layer to JNI was not handled
correctly leading to core dump. Fixed the error handling code correctly.

Also flagged three Java Objects in HTableClient for gc earlier to reduce the
java object memory usage.

Separated out the relase and flush HTableClient as two different operations
to ensure that HTableClient can be continued to be used even after flush.

Changed NAString in error routines to use the relevant heap instead of
system heap.

Change-Id: I3fac1b8de4745ec9c6f47fc8f64b483f9cc6ef36
Merge "Fix for bug 1373179"