hterm: load_tests: make browser look up handle more versions
hterm: load_tests: make browser look up handle more versions

Depending on the channel of Google Chrome you have installed, it can
have a different program name than "google-chrome".  Search for all
the standard ones and use the first one found.

Also fix quoting issues with other variables in the file.

TEST=`./bin/load_tests.sh` works with `google-chrome-stable`

Change-Id: I39e9632a35b42ac8e1a62946081f757f8662b4ab
Reviewed-on: https://chromium-review.googlesource.com/385599
Tested-by: Mike Frysinger <8f3f75c74bd5184edcfa6534cab3c13a00a2f794@chromium.org>
Reviewed-by: Rob Ginda <4419ac4e35d191308e944202d542b192188656d1@chromium.org>

chromium/hterm,chromium/hterm,chromium/hterm,chromium/hterm