Update jasper_process.py in resmoke to reflect Jasper RPC changes

The current implementation for jasper_process.py has some lines of code for handling RPC errors from Jasper when it does things like signal a process that has already terminated somehow.

This is not reflective of how Jasper actually handles such errors after the completion of MAKE-525, and therefore should be changed to check for these conditions in the val case.

Not doing this causes a test failure in replica_sets_kill_secondaries_jscore_passthrough, in which resmoke exhibits inconsistent behavior where it sends SIGKILL/SIGTERM to processes, and then expects the same processes to be alive at a later time. The full description of this problem can be found at this comment.