The "das.ignoreRedundantNetWarning" "True" thing worked for me. Yeah, I know 2 paths is best but, that's just not going to be happening at the moment. Pop up an ocasional warning. Not a constant warning that my make me less sensitive to more critical warnings.
Below is the steps to remove the configuration issue warning (No management network reduntancy) form the hosts.
Right click the cluster àClick edit settings àclick the V sphere HA and go to advance option àAdd the option and value as shown below.
Option is "das.ignoreRedundantNetWarning" and value is 'true'
Then right click each host and click Reconfigure for Vsphere HA.
just to add on something even if you find that you already have 2 or more nics set for redundancy network (and probably you have done the rest which the other posters mentioned) but the warning still persists, then you may have look at your port group settings again.
If you have vmotion enabled, re-check that your switch properties that you have the Vmotion and Management Traffic enabled (most likely its just the vmotion issue). I made this silly mistake once by not enabling it.