AMBARI-18043. Not able to proceed with RU downgrade due to spark clients failing to install (aonishuk)

ambari-common/src/main/python/resource_management/libraries/functions/version.py

@@ -42,7 +42,7 @@ def format_stack_version(input):
   if input:
     if "-" in input:
       input_array = input.split("-")
-      input = input_array[1]
+      input = input_array[0]
 
     input = re.sub(r'^\D+', '', input)
     input = re.sub(r'\D+$', '', input)

ambari-server/src/main/resources/common-services/SPARK/1.2.1/package/scripts/params.py

@@ -58,7 +58,7 @@ stack_name = status_params.stack_name
 stack_root = Script.get_stack_root()
 stack_version_unformatted = config['hostLevelParams']['stack_version']
 if upgrade_direction == Direction.DOWNGRADE:
-  stack_version_unformatted = config['commandParams']['original_stack']
+  stack_version_unformatted = config['commandParams']['original_stack'].split("-")[1]
 stack_version_formatted = format_stack_version(stack_version_unformatted)
 host_sys_prepped = default("/hostLevelParams/host_sys_prepped", False)