Test that perfdiag works when connecting to alternate endpoint with host header.
Test that perfdiag works when connecting to alternate endpoint with host header.

chriskuehl/gsutil-debian,BrandonY/gsutil,fishjord/gsutil,GoogleCloudPlatform/gsutil,dtjackson/gsutil,mattdr/gsutil,dimfeld/gsutil,craigcitro/gsutil,ttiurani/gsutil,GoogleCloudPlatform/gsutil