[SIM Fix] Fix PID file 0 issue.

Prior to this change, an empty PID file would cause the status method to return that the agent was running at PID 0.

This change ensures that an empty PID file will return a status of No
CodeDeploy Agent Running and clean up the PID file.

 * Unit Tests : Y
 * Integration Tests : N

Author: pankajtanuj

spec/aws/codedeploy/local/master_spec.rb

@@ -0,0 +1,54 @@
+require 'spec_helper'
+require_relative '../../../../vendor/gems/process_manager-0.0.13/lib/process_manager/master'
+require 'fileutils'
+
+describe ProcessManager::Daemon::Master do 
+	describe "check status" do
+  		context "PID file is empty" do
+  			it "status is nil and PID file is deleted" do
+                 # Make directory
+                 file_name = ProcessManager::Daemon::Master.pid_file
+
+                 dirname = File.dirname(file_name)
+                 unless File.directory?(dirname)
+                 	FileUtils.mkdir_p(dirname)
+                 end
+
+                 # Write empty file
+                 out_file = File.new(file_name, "w")
+                 out_file.close
+
+                 # Check that status is equal to nil and that the PID file is deleted
+                 # Note: This used to give a status of 0 but we want it to be nil
+                 expect(ProcessManager::Daemon::Master.status).to eq(nil)
+                 expect(File.exist?(file_name)).to eq(false)
+
+                 # Clean up directory
+                 FileUtils.remove_dir(dirname) if File.directory?(dirname)
+             end
+         end
+
+         context "PID file has a process that is running" do
+         	it "status is the PID number" do
+                 # Make directory
+                 file_name = ProcessManager::Daemon::Master.pid_file
+
+                 dirname = File.dirname(file_name)
+                 unless File.directory?(dirname)
+                 	FileUtils.mkdir_p(dirname)
+                 end
+
+                 # Write empty file
+                 out_file = File.new(file_name, "w")
+                 File.write(file_name, $$) # Using $$ to mock a running process
+                 out_file.close
+
+                 expect(ProcessManager::Daemon::Master.status).to eq($$)
+
+                 # Clean up and delete the file and directory
+                 File.delete(file_name) if File.exist?(file_name)
+                 FileUtils.remove_dir(dirname) if File.directory?(dirname)
+             end
+         end
+     end
+end

vendor/gems/process_manager-0.0.13/lib/process_manager/master.rb

@@ -51,7 +51,7 @@ def self.restart
 
       def self.status
         if pid = find_pid
-          if ProcessManager::process_running?(pid)
+          if pid > 0 and ProcessManager::process_running?(pid)
             pid
           else
             clean_stale_pid