AMBARI-12187. RU - Allow ignoring failures during Core Slaves in order to continue (alejandro)

ambari-server/src/main/resources/stacks/HDP/2.2/upgrades/upgrade-2.2.xml

@@ -109,6 +109,7 @@
     </group>
     
     <group name="CORE_SLAVES" title="Core Slaves" xsi:type="colocated">
+      <skippable>true</skippable>
       <service-check>false</service-check>
       <service name="HDFS">
         <component>DATANODE</component>

ambari-server/src/main/resources/stacks/HDP/2.2/upgrades/upgrade-2.3.xml

@@ -115,6 +115,7 @@
     </group>
 
     <group name="CORE_SLAVES" title="Core Slaves" xsi:type="colocated">
+      <skippable>true</skippable>
       <service-check>false</service-check>
       <service name="HDFS">
         <component>DATANODE</component>

ambari-server/src/main/resources/stacks/HDP/2.3/upgrades/upgrade-2.3.xml

@@ -133,6 +133,7 @@
     </group>
     
     <group name="CORE_SLAVES" title="Core Slaves" xsi:type="colocated">
+      <skippable>true</skippable>
       <service-check>false</service-check>
       <service name="HDFS">
         <component>DATANODE</component>