CBQE-869: modify the installer.py script to fail when installer prints out error messages

installer tracks "warning", "error", "fail" words from output, and it falls installation if they were found

Change-Id: Ic4134c7e6749d826617e90cd24065e791d459f43
Reviewed-on: http://review.couchbase.org/23546
Reviewed-by: Pavel Paulau <pavel.paulau@gmail.com>
Reviewed-by: Deepkaran Salooja <deepkaran.salooja@globallogic.com>
Reviewed-by: Andrei Baranouski <andrei.baranouski@gmail.com>
Tested-by: buildbot <build@couchbase.com>