gitsrht-update-hook: Don't exit on build submission failure

Right now the postUpdate function exits early when it fails to submit
the build manifests. This prevents the function from other tasks like
delivering webhooks.

gitsrht-update-hook/post-update.go

@@ -330,7 +330,8 @@ func postUpdate() {
 			results, err := SubmitBuild(ctx, submitter)
 			if err != nil {
 				logger.Printf("Error submitting build job: %v", err)
-				log.Fatalf("Error submitting build job: %v", err)
+				log.Printf("Error submitting build job: %v", err)
+				continue
 			}
 			if len(results) == 0 {
 				continue