ACCUMULO-3215 Ensure that ImportTable writes absolute paths, not relative.

ImportExportIT creates a table, exports it and then imports it to the
same instance to ensure that the imported copy is equivalent
to the original. Without the changes to ImportTable, the test failed
because the copy was unusable due to incorrect metadata table entries.
Merge branch '1.6'

Conflicts:
	server/master/src/main/java/org/apache/accumulo/master/tableOps/ImportTable.java