Add _[no]red suffix to RampUpTests.

For the RampUpTest.UpDownUpAbsSendTimeSimulcastRedRtx and
RampUpTest.UpDownUpTransportSequenceNumberRtx [1,2], the generated metric names
are the same:

- ramp_up_down_up_3streams_rtx.first_rampup
- ramp_up_down_up_3streams_rtx.second_rampup
- ramp_up_down_up_3streams_rtx.rampdown

So only one of the two tests (whichever ran last) has its metrics reported to
the perf dashboard, while the others has its metrics ignored.

[1] https://webrtc.googlesource.com/src/+/master/call/rampup_tests.cc#571
[2] https://webrtc.googlesource.com/src/+/master/call/rampup_tests.cc#579

Bug: webrtc:8691
Change-Id: I632dfe32d3b4729f1b0233c44d03c2894ee8c027
Reviewed-on: https://webrtc-review.googlesource.com/36941
Reviewed-by: Patrik Höglund <phoglund@webrtc.org>
Reviewed-by: Henrik Andreassson <henrika@webrtc.org>
Commit-Queue: Edward Lemur <ehmaldonado@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21499}
diff --git a/call/rampup_tests.cc b/call/rampup_tests.cc
index 1d58419..d035416 100644
--- a/call/rampup_tests.cc
+++ b/call/rampup_tests.cc
@@ -461,7 +461,9 @@
     str += "_";
   }
   str += (rtx_ ? "" : "no");
-  str += "rtx";
+  str += "rtx_";
+  str += (red_ ? "" : "no");
+  str += "red";
   return str;
 }