Description of problem:
Memory penalty always work on hosts without engine vm

Version-Release number of selected component (if applicable):
ovirt-hosted-engine-ha-1.3.1-1.el7ev.noarch

How reproducible:
Always

Steps to Reproduce:
1. Deploy hosted engine on two hosts
2. Run hosted-engine --vm-status
3.

Actual results:
Host with vm have score 3400, host without vm have score 3000

Expected results:
Both hosts have score 3400

Additional info:
Problem in:
@property
def min_memory_threshold(self):
    return int(self._config.get(config.VM, config.MEM_SIZE))
it return tuple (4096, ) and not integer