ctdb-tests: Update preamble for INTEGRATION tests

ctdb-tests: Update preamble for INTEGRATION tests

* Use "#!/usr/bin/env bash" for improved portability

* Drop test_info() definition and replace it with a comment

  The use of test_info() is pointless.

* Drop call to cluster_is_healthy()

  This is a holdover from when the previous test would restart daemons
  to get things ready for a test.  There was also a bug where going
  into recovery during the restart would sometimes cause the cluster
  to become unhealthy.  If we really need something like this then we
  can add it to ctdb_test_init().

* Make order of preamble consistent

Signed-off-by: Martin Schwenke <martin@meltin.net>