Description of problem:

SD master/spm selection will be done on uptime and cpu load. 
if we have a SD that we rarely use because it's not as powerful as the rest but has been up for a long period of time, that Domain will be selected as a Master because of uptime and cpu load. 

Version-Release number of selected component (if applicable):

si15

How reproducible:


Steps to Reproduce:
1. create a small unused storage domain on an old host
2. reboot the rest of the hosts and load them with vm's 
3. block connectivity to the storage from spm
  
Actual results:

we would select host based on cpu load and uptime. 

Expected results:

we should fine tune the selection

Additional info: