Use lists for tags instead of dicts

gns3server/db/models/templates.py

@@ -36,7 +36,7 @@ class Template(BaseTable):
     builtin = Column(Boolean, default=False)
     usage = Column(String)
     template_type = Column(String)
-    tags = Column(JSON, default='{}')
+    tags = Column(JSON)
     compute_id = Column(String)
     images = relationship("Image", secondary=image_template_map, back_populates="templates")