Serve api51. on devserver

Summary:
Split api. and api51. definitions, as api. is for web-001
while api51. is for WindRiver.

Ref T1897

Test Plan:

• nginx -t
• Browse https://api51.nasqueron.org/, got a 200
• Browse https://api51.nasqueron.org/servers-log, got a 418

Reviewers: dereckson

Reviewed By: dereckson

Maniphest Tasks: T1897

Differential Revision: https://devcentral.nasqueron.org/D3172