Allow OWNERS file with single owner

When there is a single owner in the OWNERS file
the resulting element is a single JSON String rather
than an Array and thus needs to be returned as a Stream
of a single element.

Change-Id: I4dcf1fcca383ce0745ef953a285371e4f083a0bd
diff --git a/owners-common/src/main/java/com/vmware/gerrit/owners/common/ConfigurationParser.java b/owners-common/src/main/java/com/vmware/gerrit/owners/common/ConfigurationParser.java
index 2b8ecc9..17f75d0 100644
--- a/owners-common/src/main/java/com/vmware/gerrit/owners/common/ConfigurationParser.java
+++ b/owners-common/src/main/java/com/vmware/gerrit/owners/common/ConfigurationParser.java
@@ -80,6 +80,9 @@
   }
 
   private static Stream<String> extractOwners(JsonNode node) {
+    if(node.isTextual()) {
+      return Stream.of(node.asText());
+    }
     return iteratorStream(node.iterator()).map(JsonNode::asText);
   }