Add mac / linux trigger phrases

This restores the ability to utter the following test phrases:

- test mac please
- test linux please

netci.groovy

@@ -121,7 +121,7 @@ commitPullList.each { isPr ->
   }
 
   def triggerPhraseOnly = false
-  def triggerPhraseExtra = ""
+  def triggerPhraseExtra = "linux"
   Utilities.setMachineAffinity(myJob, 'Ubuntu14.04', 'latest-or-auto')
   Utilities.addXUnitDotNETResults(myJob, '**/xUnitResults/*.xml')
   addRoslynJob(myJob, jobName, branchName, isPr, triggerPhraseExtra, triggerPhraseOnly)
@@ -139,7 +139,7 @@ commitPullList.each { isPr ->
   }
 
   def triggerPhraseOnly = true
-  def triggerPhraseExtra = ""
+  def triggerPhraseExtra = "mac"
   Utilities.addXUnitDotNETResults(myJob, '**/xUnitResults/*.xml')
   addRoslynJob(myJob, jobName, branchName, isPr, triggerPhraseExtra, triggerPhraseOnly)
 }