rbd: copy creds when copying the connection

rbd flatten functions is a CLI call and it expects
the creds as the input and copying of creds is
required when we generate the temp clone image.

Signed-off-by: Madhu Rajanna <madhupr007@gmail.com>
(cherry picked from commit 916c97b4a8)

internal/util/connection.go

@@ -81,6 +81,7 @@ func (cc *ClusterConnection) Copy() *ClusterConnection {
 	c := ClusterConnection{}
 	c.discardOnZeroedWriteSameDisabled = cc.discardOnZeroedWriteSameDisabled
 	c.conn = connPool.Copy(cc.conn)
+	c.Creds = cc.Creds
 
 	return &c
 }