testing global gerrit.

I will submit this via the below RPC to verify that Global Gerrit can submit a change, bypassing any lingering errors with Gobble routing and mendel experiments (b/519715863).

stubby --dapper_trace_period=1 --print_trace_url call blade:gerrit HTTPOverRPC.HTTPRequest << 'EOF'
text: "POST /a/changes/634277/submit HTTP/1.1\r\nHost: gerrit-review.git.corp.google.com\r\nX-GFE-SSL: yes\r\nContent-Length: 0\r\n\r\n"
EOF

Change-Id: Iaea3c0dbb20c3c6fff9fc559d7cb942e1f03bc92