Bump up the API version to 3

Since we add the package name to the protocol buffer.
The new protocol buffer is not compatible to the old protocl buffer
because the rpc call path changes.
Update the backing image manager API version to 3.

Signed-off-by: JenTing Hsiao <jenting.hsiao@suse.com>

pkg/meta/version.go

@@ -3,8 +3,8 @@ package meta
 const (
 	// BackingImageManagerAPIVersion used to communicate with the user
 	// \e.g. longhorn-manager
-	BackingImageManagerAPIVersion    = 2
-	BackingImageManagerAPIMinVersion = 2
+	BackingImageManagerAPIVersion    = 3
+	BackingImageManagerAPIMinVersion = 3
 )
 
 // Following variables are filled in by main.go