client.skia: allow is_production_host to be determined automatically
client.skia: allow is_production_host to be determined automatically

This enables the default behavior where is_production_host is True on the
production master and False elsewhere.  It will enable the http_status_push
functionality.

BUG=skia:761

Review URL: https://codereview.chromium.org/467253002

git-svn-id: 239fca9b83025a0b6f823aeeca02ba5be3d9fd76@289362 0039d316-1c4b-4281-b951-d872f2087c98

eunchong/build,eunchong/build,eunchong/build,eunchong/build