CBQE-1882: Improvement in install.py to get builds from respective index.html rather than all builds

Change-Id: I27133b4b71e80489d3299f14d27b972626f8619b
Reviewed-on: http://review.couchbase.org/32673
Reviewed-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>
Tested-by: Sangharsh Agarwal <sangharsh.agarwal@globallogic.com>