membase-cli server-list output should show clusterMembershipStatus

The current output of membase server-list is...

$ ./membase server-list -c 10.104.109.242:8080
ns_1@10.104.109.242 healthy
ns_1@10.214.126.144 healthy
ns_1@10.254.38.176 healthy

It should instead also show the cluster-membership-status, like...

$ ./membase server-list -c 10.104.109.242:8080
ns_1@10.104.109.242 healthy active
ns_1@10.214.126.144 healthy active
ns_1@10.254.38.176 healthy pending-add

Notice that I reduced the about of spaces, too, to be more terse and parsable by other programs.