Add suppression for "uninitialized memory" error in getaddrinfo.

tools_webrtc/valgrind/memcheck/suppressions.txt

Index: tools_webrtc/valgrind/memcheck/suppressions.txt
diff --git a/tools_webrtc/valgrind/memcheck/suppressions.txt b/tools_webrtc/valgrind/memcheck/suppressions.txt
index ed3b2617d621ec3a18f842a7b49ed9097bca6605..ef6d09fd83d08296a74fce5ae06ac910ab8576af 100644
--- a/tools_webrtc/valgrind/memcheck/suppressions.txt
+++ b/tools_webrtc/valgrind/memcheck/suppressions.txt
@@ -27,6 +27,20 @@
    fun:snprintf
    ...
 }
+# See: https://bugs.chromium.org/p/webrtc/issues/detail?id=7973
+{
+   libc_getaddrinfo_uninitialized
+   Memcheck:Param
+   sendmsg(mmsg[0].msg_hdr)
+   fun:sendmmsg
+   fun:__libc_res_nsend
+   fun:__libc_res_nquery
+   fun:__libc_res_nsearch
+   fun:_nss_dns_gethostbyname4_r
+   fun:gaih_inet
+   fun:getaddrinfo
+   ...
+}
 
 #-----------------------------------------------------------------------
 # webrtc stuff