hang_analyzer.py should send a SIGUSR1 to resmoke.py before attaching to any processes

There are cases where we trigger the 15-minute "post" phase Evergreen timeout with GDB getting stuck while attached to a process. We should send a SIGUSR1 signal to resmoke.py as the first thing buildscripts/hang_analyzer.py does to ensure that we are generating a report.json file (and therefore populating the Evergreen sidebar) as often as we possibly can.