ACCUMULO-1961 Fix/remove some more trivial warnings
ACCUMULO-2114 Move built-in namespace names to a method
ACCUMULO-2317 Apply ClientOpts fix to shell also
ACCUMULO-1989 Use default namespace name explicitly in shell
ACCUMULO-2092 Make client view of table existence consistent

  Clear the cache after exceptions, instead of just successful fate
  operations. This ensures that a failure as the result of a
  TableNotFoundException or TableExistsException will be consistent with
  the client's view, if they check it right after the failure.
Merge remote-tracking branch 'origin/1.6.0-SNAPSHOT'