membase-cli is now couchbase-cli, healthchecker added

A recent commit (abf3b345bb7fdea9f650ee8b416085df7e75f5db)
on the top level Makefile [1] broke the build bots as they
run `make clean-xdf-hard` which traverses down directories.
One of the expected ones is now couchbase-cli and
healthchecker.

[1] https://github.com/couchbase/tlm/commit/abf3b345bb7fdea9f650ee8b416085df7e75f5db

Change-Id: I811a8fcfdc00509c87f4f142b627cec6bc719329
Reviewed-on: http://review.couchbase.org/26477
Reviewed-by: Philip Labee <philip@couchbase.com>
Tested-by: Philip Labee <philip@couchbase.com>