Suppress memcheck errors on linux bot.

BUG=

Review-Url: https://codereview.webrtc.org/2278183002
Cr-Commit-Position: refs/heads/master@{#13932}

tools/valgrind-webrtc/memcheck/suppressions.txt

diff --git a/tools/valgrind-webrtc/memcheck/suppressions.txt b/tools/valgrind-webrtc/memcheck/suppressions.txt
index 28ab276..d6ab807 100644
--- a/tools/valgrind-webrtc/memcheck/suppressions.txt
+++ b/tools/valgrind-webrtc/memcheck/suppressions.txt
@@ -263,6 +263,20 @@
    fun:WebRtcNetEQ_GetSpeechOutputType
    ...
 }
+{
+   vfprintf
+   Memcheck:Uninitialized
+   fun:vfprintf
+   fun:vsnprintf
+   fun:snprintf
+   ...
+   fun:_ZNK7testing8internal18FunctionMockerBaseIFbRKN6webrtc4rtcp17TransportFeedbackEEE32UntypedDescribeUninterestingCallEPKvPSo
+   fun:_ZN7testing8internal25UntypedFunctionMockerBase17UntypedInvokeWithEPKv
+   fun:_ZN6webrtc11MockRtpRtcp18SendFeedbackPacketERKNS_4rtcp17TransportFeedbackE
+   fun:_ZN6webrtc12PacketRouter12SendFeedbackEPNS_4rtcp17TransportFeedbackE
+   fun:_ZN6webrtc34PacketRouterTest_SendFeedback_Test8TestBodyEv
+}
+
 
 #-----------------------------------------------------------------------
 # libjingle stuff (talk folder)