CBQE-1026: installation hangs - 2 potential issues

seems like there are 2 potential issues here:

1) syntax 'log.error(downloaded, 'unable to download binaries : {0}'.format(build.url))' is not correct
+ return False( installation should be failed if remote_client.download_build(build) returned False)
2)channel hangs - better to add timeout

Change-Id: I7f81fba5f61a381071c3dffe7fc1b880f157ffeb
Reviewed-on: http://review.couchbase.org/24402
Tested-by: buildbot <build@couchbase.com>
Reviewed-by: Pavel Paulau <pavel.paulau@gmail.com>