Updates the example servers to use #run_till_terminated

src/ruby/bin/interop/interop_server.rb

@@ -185,7 +185,7 @@ def main
     logger.info("... running insecurely on #{host}")
   end
   s.handle(TestTarget)
-  s.run
+  s.run_till_terminated
 end
 
 main

src/ruby/bin/math_server.rb

@@ -183,7 +183,7 @@ def main
   end
 
   s.handle(Calculator)
-  s.run
+  s.run_till_terminated
 end
 
 main

src/ruby/bin/noproto_server.rb

@@ -105,7 +105,7 @@ def main
   end
 
   s.handle(NoProto)
-  s.run
+  s.run_till_terminated
 end
 
 main