change: Just run the required command and let the exception do the rest

if the process died. Checking first if the process is still alive proofed
to be quite error prone, atleast on a rather slow compute node.

cloudinit/config/cc_power_state_change.py

@@ -31,16 +31,12 @@ frequency = PER_INSTANCE
 EXIT_FAIL = 254
 
 #
-# Returns the cmdline for the given process id.
+# Returns the cmdline for the given process id. In Linux we can use procfs for
+# this but on BSD there is /usr/bin/procstat.
 #
 
 def givecmdline(pid):
-    # Check if this pid still exists by sending it the harmless 0 signal.
     try:
-        os.kill(pid, signal.SIG_DFL)
-    except OSError:
-        return None
-    else:
         # Example output from procstat -c 1
         #   PID COMM             ARGS
         #     1 init             /bin/init --
@@ -51,6 +47,8 @@ def givecmdline(pid):
             return m.group(2)
         else:
             return util.load_file("/proc/%s/cmdline" % pid)
+    except IOError:
+        return None
 
 def handle(_name, cfg, _cloud, log, _args):