(MODULES-2244) Update rake task to remove WaitFor DSC Resources

Update rake task to remove any WaitFor DSC Resources downloaded from the
upstream DSCResources repo. We cannot support these types of DSC
Resources at this time, so add a filter to remove them after we clone
the PowerShell DSCResources repo. As a last failsafe, we check after
this task for any Waitfor resources and fail the build if they are
present.

build/dsc.rake

@@ -110,8 +110,8 @@ eod
     task :build, [:module_path] do |t, args|
       module_path = args[:module_path] || default_dsc_module_path
       m = Dsc::Manager.new
-      wait_for_resources = Dir["#{module_path}/**/*WaitFor*"]
-      fail "WaitFor* resources found - aborting type building!\n\n#{wait_for_resources}\n" if !wait_for_resources.empty?
+      wait_for_resources = Dir["#{module_path}/**/MSFT_WaitFor*"]
+      fail "MSFT_WaitFor* resources found - aborting type building! Please remove the following MSFT_WaitFor* DSC Resources and run the build again.\n\n#{wait_for_resources}\n" if !wait_for_resources.empty?
       m.target_module_path = module_path
       msgs = m.build_dsc_types
       msgs.each{|m| puts "#{m}"}