don't fail restarting delayed jobs if the pid file is orphaned

previously, delayed_job restart/stop would fail if the pid file was
there, but the process didn't exist

test plan: start delayed jobs, then kill -9 the pool. then try
restarting delayed jobs, it'll still be successful.

Change-Id: Iaedbdc6c0381a6f79ab488eefd19344645e3e2df
Reviewed-on: https://gerrit.instructure.com/8266
Reviewed-by: Brian Palmer <brianp@instructure.com>
Reviewed-by: Cody Cutrer <cody@instructure.com>
Tested-by: Hudson <hudson@instructure.com>

vendor/plugins/delayed_job/lib/delayed/pool.rb

@@ -219,7 +219,11 @@ class Pool
     pid = File.read(pid_file) if File.file?(pid_file)
     if pid.to_i > 0
       puts "Stopping pool #{pid}..."
-      Process.kill('INT', pid.to_i)
+      begin
+        Process.kill('INT', pid.to_i)
+      rescue Errno::ESRCH
+        # ignore if the pid no longer exists
+      end
     else
       status
     end
@@ -227,12 +231,13 @@ class Pool
 
   def status(print = true)
     pid = File.read(pid_file) if File.file?(pid_file)
-    if pid
+    alive = pid && pid.to_i > 0 && Process.kill(0, pid.to_i) rescue false
+    if alive
       puts "Delayed jobs running, pool PID: #{pid}" if print
     else
       puts "No delayed jobs pool running" if print
     end
-    pid.to_i > 0 ? pid.to_i : nil
+    alive
   end
 
   def read_config(config_filename)