Fix arguments for calls to Ruby's `Time.at`

`Time.at` takes microseconds as a second arg, not nanoseconds. Fixes
conversion of deadline time on the server-side.
diff --git a/src/ruby/ext/grpc/rb_grpc.c b/src/ruby/ext/grpc/rb_grpc.c
index 188a624..dfcc95b 100644
--- a/src/ruby/ext/grpc/rb_grpc.c
+++ b/src/ruby/ext/grpc/rb_grpc.c
@@ -220,7 +220,7 @@
                        time_const);
   real_time = gpr_convert_clock_type(*time_const, GPR_CLOCK_REALTIME);
   return rb_funcall(rb_cTime, id_at, 2, INT2NUM(real_time.tv_sec),
-                    INT2NUM(real_time.tv_nsec));
+                    INT2NUM(real_time.tv_nsec / 1000));
 }
 
 /* Invokes inspect on the ctime version of the time val. */
diff --git a/src/ruby/ext/grpc/rb_server.c b/src/ruby/ext/grpc/rb_server.c
index bf26841..2a6a246 100644
--- a/src/ruby/ext/grpc/rb_server.c
+++ b/src/ruby/ext/grpc/rb_server.c
@@ -218,7 +218,7 @@
       grpc_rb_sNewServerRpc, rb_str_new2(st.details.method),
       rb_str_new2(st.details.host),
       rb_funcall(rb_cTime, id_at, 2, INT2NUM(deadline.tv_sec),
-                 INT2NUM(deadline.tv_nsec)),
+                 INT2NUM(deadline.tv_nsec / 1000)),
       grpc_rb_md_ary_to_h(&st.md_ary), grpc_rb_wrap_call(call, call_queue),
       NULL);
   grpc_request_call_stack_cleanup(&st);