pcp-dstat: no stack trace when dstat exits due to a signal
pcp-dstat: no stack trace when dstat exits due to a signal

Prevent generation of a python stack trace when dstat exits
due to sighup or sigterm via the pmconfig.py signal handling
code.

Resolves Red Hat bugzilla #1768619

adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp,adfernandes/pcp