ACCUMULO-3405 Bump findbugs-maven-plugin to 3.0.0
Merge branch '1.6'
ACCUMULO-3400 Add sanity check for VolumeChooser return

  Backports the sanity check from ACCUMULO-3393 to 1.6. Ensures that
  VolumeChoosers only choose from the available options, and don't manifest
  choices of their own to return, which aren't available.
Merge branch '1.6'
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-2815 wip.
Move around some more stuff
Rip out the doAs from the UGIAssumingProcessor and just track the principal.

Try to approach this as the client address is done. Pull the principal
out of the Sasl server and store it so we can use it to make
a proper TCredentials that will hopefully be seamless for
the other server processes to use (with the Authenticator/Authorizor).
Stub out a shell kerberos authentication token.
ACCUMULO-2815 Stub out a SaslConnectionParams for kerberos.
ACCUMULO-2815 get the fqdn for the host, not just whats in the HostAndPort.
ACCUMULO-2815 Stub out an invocation handler to update the principal from SASL into the tcredentials.

I think this should be an appropriate way to ensure that clients can't attempt to act
as a user other than themself. We can override whatever was passed in via the RPC,
rely on SASL/GSSAPI giving us the proper principal from kerberos and using that
as the principal for authorization (and skipping more authentication later).
ACCUMULO-2815 Wrap all thrift servers in the new proxy

Ensures that the TCredentials is updated properly before
any server interface implementation will see it.
ACCUMULO-2815 Start to stub out SecurityOperation changes.

Need to correctly handle users authenticated by SASL/GSSAPI
as well as the SYSTEM user.
Update the client code to pull the server principal to set up the SASL transport.
ACCUMULO-2815 Try to introduce a required admin user acct during init with security
ACCUMULO-2815 Use enum correctly.
ACCUMULO-2815 Throw the exception when security *isn't* enabled..