Several minor fixes (#47)

Several minor fixes:
- raid_array check should return an empty array, not NoneType
- not all systems will have IPv6 defined, handle this case
- Vendor Supermicro was incomplete.

netbox_agent/vendors/supermicro.py

@@ -3,8 +3,14 @@ from netbox_agent.server import ServerBase
 
 
 class SupermicroHost(ServerBase):
+    def __init__(self, *args, **kwargs):
+        super(SupermicroHost, self).__init__(*args, **kwargs)
+        self.manufacturer = 'Supermicro'
+
     def is_blade(self):
-        return self.get_product_name().startswith('SBI')
+        blade = self.get_product_name().startswith('SBI')
+        blade |= self.get_product_name().startswith('SYS')
+        return blade
 
     def get_blade_slot(self):
         if self.is_blade():