[HWKMETRICS-721] Update the order of metric updates to ensure the met…

…rics is persisted on the metrics index prior to updating the tags. This will resolve corner cases where an update fails and the tags of a metric are persisted without the metric definition properly persisted.

(cherry picked from commit 5c990b2)
Signed-off-by: Stefan Negrea <snegrea@redhat.com>
(cherry picked from commit 378902d)
Signed-off-by: Stefan Negrea <snegrea@redhat.com>

# Conflicts:
#	core/metrics-core-service/src/main/java/org/hawkular/metrics/core/service/MetricsServiceImpl.java

core/metrics-core-service/src/main/java/org/hawkular/metrics/core/service/MetricsServiceImpl.java

@@ -578,7 +578,7 @@ public Observable<Void> addTags(Metric<?> metric, Map<String, String> tags) {
             return Observable.error(e);
         }
 
-        return dataAccess.addTags(metric, tags).mergeWith(dataAccess.insertIntoMetricsTagsIndex(metric, tags))
+        return dataAccess.insertIntoMetricsTagsIndex(metric, tags).concatWith(dataAccess.addTags(metric, tags))
                 .toList().map(l -> null);
     }