Tolerate missing Chrome in site_sysinfo

Many ChromeOS Core boards don't have Chrome.

BUG=None
TEST=Ran test against Chrome-less board, no more error messages
about missing Chrome.

Change-Id: I9f58f5abf553b54d93cd932dec782e9d709fe547
Reviewed-on: https://chromium-review.googlesource.com/218879
Tested-by: Christopher Wiley <wiley@chromium.org>
Reviewed-by: Fang Deng <fdeng@chromium.org>
Commit-Queue: Christopher Wiley <wiley@chromium.org>
1 file changed