yb-admin should not show a FATAL with a stack trace if it is unable to contact master leader

[mbautin]

Jira Link: DB-2354
F20190607 16:58:04 ../../src/yb/tools/yb-admin_client.cc:165] Check failed: _s.ok() Bad status: Timed out (yb/rpc/rpc.cc:199): Could not locate the leader master: GetLeaderMasterRpc(addrs: [127.0.0.1:7100], num_attempts: 336) passed its deadline 14656.514s (passed: 60.128s)
@ 0x10cd76500 google::LogDestination::LogToSinks()
@ 0x10cd7550b google::LogMessage::SendToLog()
@ 0x10cd75eb5 google::LogMessage::Flush()
@ 0x10cd7a9bf google::LogMessageFatal::~LogMessageFatal()
@ 0x10cd76ea9 google::LogMessageFatal::~LogMessageFatal()
@ 0x109480638 yb::tools::ClusterAdminClient::Init()
@ 0x1094a7237 yb::tools::enterprise::ClusterAdminClient::Init()
@ 0x10949d4e1 yb::tools::ClusterAdminCli::Run()
@ 0x10949f342 main
@ 0x7fff73f33ed9 start