Add a test case for accidental addition, removal and the re-addition of a master

Quoting aserbin from code review for remove master CLI
https://gerrit.cloudera.org/c/17010/9/src/kudu/master/dynamic_multi_master-test.cc#1202

Not sure I missed a test I was looking for, but what do you think about adding a test for a use case when first a new master is added mistakenly (say, using a valid, but not intended host), and then rolling back such a change, targeting to run 'kudu add master' again with correct destination node?

That's about having a sequence of 'kudu master add <master_rpc_addresses> <new_master_mistaken_address>', immediately followed by 'kudu master remove <master_rpc_addresses> <new_master_mistaken_address>'?