CBQE-0: fix 'sudo: cd: command not found' in healthchecker_test

Change-Id: I1ba09eb20a159374374ca27977dde3578c6f63ee
Reviewed-on: http://review.couchbase.org/30261
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: Andrei Baranouski <andrei.baranouski@gmail.com>