ACCUMULO-3421 Retry initialization of trace client

If we fail to connect to ZK for some reason,
we will never get the watcher set and tracing will
never be initialized properly. Add a simple retry
to ensure that it happens.
ACCUMULO-3424 Remove requirement for properties on provided token.
Merge branch '1.6'
ACCUMULO-???? Drop Hadoop 1 support
ACCUMULO-2589 Drop deprecated code from 1.x
ACCUMULO-2589 Bump version to 2.0.0

  Incompatible API changes; requires major version number bump
WIP - new module