This warning occurs in the Compute log if you do not have the optional multipath-tools package installed on the compute node. This is an optional package and the volume attachment does work without the multipath tools installed. If the multipath tools package is installed on the compute node, it is used to perform the volume attachment. The IDs in your message are unique to your system.
Install the multipath-tools package on the compute node.
$ apt-get install multipath-tools //Ubuntu
$ Yum install multipath-tools //CentOS/RHEL
Hope this will help you.