[autotest] Modify test_that to figure out the board of the remote host.

Test_that currently relies on the user for the --board argument. This cl
teaches test_that to ssh into a DUT and find the board, if one isn't
specified.

TEST=Invoked test_that dummy_Pass with and without a board, with and without a
     resutls dir, on DUTs with different boards.
BUG=chromium:265705
CQ-DEPEND=CL:I50811eb8b0e6b145a190211391c2409913bc8a33

Change-Id: I0b12bb456c8f032266c7530a39f87cefc5d9182b
Reviewed-on: https://chromium-review.googlesource.com/169767
Tested-by: Prashanth B <beeps@chromium.org>
Reviewed-by: Aviv Keshet <akeshet@chromium.org>
Commit-Queue: Prashanth B <beeps@chromium.org>
diff --git a/server/site_utils.py b/server/site_utils.py
index 6b27970..f3acdb7 100644
--- a/server/site_utils.py
+++ b/server/site_utils.py
@@ -87,13 +87,13 @@
             url_content = base_utils.urlopen('%s%s'% (
                 _CHROMIUM_BUILD_URL, sheriff_js)).read()
         except (ValueError, IOError) as e:
-            logging.error('could not parse sheriff from url %s%s: %s',
-                           _CHROMIUM_BUILD_URL, sheriff_js, str(e))
+            logging.warning('could not parse sheriff from url %s%s: %s',
+                             _CHROMIUM_BUILD_URL, sheriff_js, str(e))
         else:
             ldaps = re.search(r"document.write\('(.*)'\)", url_content)
             if not ldaps:
-                logging.error('Could not retrieve sheriff ldaps for: %s',
-                               url_content)
+                logging.warning('Could not retrieve sheriff ldaps for: %s',
+                                 url_content)
                 continue
             sheriff_ids += ['%s@chromium.org' % alias.replace(' ', '')
                             for alias in ldaps.group(1).split(',')]