Update ruby perf code with keyword args changes

src/ruby/qps/client.rb

@@ -66,8 +66,10 @@ class BenchmarkClient
         cred = GRPC::Core::ChannelCredentials.new()
       end
       if config.security_params.server_host_override
-        opts[GRPC::Core::Channel::SSL_TARGET] =
+        channel_args = {}
+        channel_args[GRPC::Core::Channel::SSL_TARGET] =
           config.security_params.server_host_override
+        opts[:channel_args] = channel_args
       end
     else
       cred = :this_channel_is_insecure

src/ruby/qps/server.rb

@@ -75,13 +75,14 @@ class BenchmarkServer
     @port = @server.add_http2_port("0.0.0.0:" + port.to_s, cred)
     @server.handle(BenchmarkServiceImpl.new)
     @start_time = Time.now
-    Thread.new {
+    t = Thread.new {
       @server.run
     }
+    t.abort_on_exception
   end
   def mark(reset)
     s = Grpc::Testing::ServerStats.new(time_elapsed:
-                                         (Time.now-@start_time).to_f)
+                                       (Time.now-@start_time).to_f)
     @start_time = Time.now if reset
     s
   end