Description of problem:
the opta planner is recommend to migrate vm. after i click to migrate the vm, i get this error : Status: Migration start failed (409): [Cannot migrate VM. There is no host that satisfies current scheduling constraints. See below for details:, The host host_mixed_1 did not satisfy internal filter Memory because has availabe 912 MB memory. Insufficient free memory to run the VM.]

Version-Release number of selected component (if applicable):
optimizer should not suggest migrate VM that can't be migrated. 

How reproducible:
100%

Steps to Reproduce:
1. have a setup with two hosts and optimizer installed 
2. create a  big VM that consumed (almost) the Max free Memory for scheduling new VMs (to be less then 1GB) for example (if i have VM with 16G memory, then create Vm with 15G memory)
3. create 6 vm with 1BG memory 
4. optimizer will recommend to migrate a vm, try to migrate the vm and the you will get this error : 
Status: Migration start failed (409): [Cannot migrate VM. There is no host that satisfies current scheduling constraints. See below for details:, The host host_mixed_1 did not satisfy internal filter Memory because has availabe 912 MB memory. Insufficient free memory to run the VM.]

Actual results:
will get this error : 
Status: Migration start failed (409): [Cannot migrate VM. There is no host that satisfies current scheduling constraints. See below for details:, The host host_mixed_1 did not satisfy internal filter Memory because has availabe 912 MB memory. Insufficient free memory to run the VM.]


Expected results:
optimizer should not suggest migrate VM that can't be migrated. 

Additional info: