dtest/killall.py: fix pid file unlink race
dtest/killall.py: fix pid file unlink race

* run pid file remove remotely, not locally (d'oh)

* don't complain if pid file can't be removed; this is very normal and
expected, since the application is supposed to clean up its own pid file
anyway.

Signed-off-by: Colin McCabe <3142ce8a0bdba4a38073365893e6b74f72d9c512@alumni.cmu.edu>

cmccabe/redfish,cmccabe/redfish,cmccabe/redfish,cmccabe/redfish,cmccabe/redfish