[gitaly-wrapper] Check process binary before adoption

The PID written in pidfile may be a reassigned by the kernel to another process and gitaly-wrapper will not start a new gitaly instance.

This MR checks if the process path basename is gitaly before adopting a child process.

Closes #1661 (closed)

This bug was introduced in gitaly 1.33.0

$ git show v11.9.11:GITALY_SERVER_VERSION
1.27.2

$ git show v11.10.4:GITALY_SERVER_VERSION
1.34.1

It has to be backported on %11.11 and in %11.10 if we plan to release 11.10.5.