Relax branch restriction while making release

Previously making release of non-library project from non-master branch
would fail. Relax this check to facilitate submission to gerrit via
topic branches.

Change-Id: Ie89b79a45033bee422e4ff898069ea6ac2c2f524
Related: OS#1861
diff --git a/osmo-release.mk b/osmo-release.mk
index 4407c86..3fe6803 100644
--- a/osmo-release.mk
+++ b/osmo-release.mk
@@ -10,7 +10,7 @@
 endif
 	@echo "Releasing" $(VERSION) "->" $(NEW_VERSION)"..."
 ifeq ($(LIBVERS),)
-	@gbp dch --debian-tag='%(version)s' --auto --meta --git-author --multimaint-merge
+	@gbp dch --debian-tag='%(version)s' --auto --meta --git-author --multimaint-merge --ignore-branch
 else
 	@echo "You should NOT be doing this unless you've read and understood following article:"
 	@echo "https://www.gnu.org/software/libtool/manual/html_node/Updating-version-info.html#Updating-version-info"