Print warning when there are not enough zone for EC

[sirio81]

Hi, this is the warning I get if I try to format the cluster with -c 2:1 and only two nodes.

dog cluster format -c 2:1
Number of copies (3) is larger than number of nodes (2).
Are you sure you want to continue? [yes/no]: ^C
dog node list
  Id Host:Port V-Nodes Zone
   0 192.168.2.44:7000 3 738371776
   1 192.168.2.45:7000 3 755148992
dog cluster format -c 2:1
Number of copies (3) is larger than number of nodes (2).
Are you sure you want to continue? [yes/no]:

I think the same logic shall apply when the zone number is not enough like in this example:

dog node list
  Id Host:Port V-Nodes Zone
   0 192.168.2.44:7000 3 1
   1 192.168.2.45:7000 3 1
   2 192.168.2.46:7000 3 2
   3 192.168.2.47:7000 3 2
dog cluster format -c 2:1
using backend plain store

It should print the warning.