multiversion: test we emit Invalid host name

Whenever a host headers is unrecognized, we are sending a error message
back to the client and generate a error_log.  Add a test for it, PHPUnit
converts PHP errors as a PHPUnit_Framework_Error exception.

Bug: 69419
Change-Id: I544b19861ad3bf6c2a932eae8114ec8da0725b41
Merge "multiversion: test we emit Invalid host name"