Fixed host free memory checking
Fixed host free memory checking

MEM_USAGE is total allocated memory, but not a real used memory, so even if host has half of free memory, cvem decided to migrate some vms...

Signed-off-by: Kristián Feldsam <78459458b5fb7d69b49c35965228fab7849e1b4d@gmail.com>

grycap/cloudvamp,grycap/cloudvamp,grycap/cloudvamp