Tool Labs: Bump max_user_connections to 512

Some tools hitting into the 10 limit really easy.  512 is a lot
but should allow the occasional peak use (which is needed for
a number of tools with incoming links from the projects)

Bug: 49872

Change-Id: I5bf9c67b162764d4f3da011ff36391c0e714a804
Merge "Tool Labs: Bump max_user_connections to 512" into production