add set_primary command to sharectl

make it easy to switch the elasticsearch index used for search:
```
sharectl search set_primary <index_name>
```

share/bin/search.py

@@ -58,6 +58,14 @@ def setup(args, argv):
         elastic_manager.update_primary_alias(primary_index)
 
 
+@search.subcommand('Set the "primary" index used to serve search results')
+def set_primary(args, argv):
+    """
+    Usage: {0} search set_primary <index_name>
+    """
+    ElasticManager().update_primary_alias(args['<index_name>'])
+
+
 @search.subcommand('Start the search indexing daemon')
 def daemon(args, argv):
     """

share/search/elastic_manager.py

@@ -94,7 +94,7 @@ def update_primary_alias(self, primary_index_name):
             pass
 
         if previous_indexes == [primary_index_name]:
-            logger.info(f'index {primary_index_name} is already the primary')
+            logger.warn(f'index {primary_index_name} is already the primary')
             return
 
         logger.warn(f'removing aliases to {previous_indexes} and adding alias to {primary_index_name}')