Suppress yet another wrong-locking report in NSS

tools/valgrind/tsan/suppressions.txt

Index: tools/valgrind/tsan/suppressions.txt
===================================================================
--- tools/valgrind/tsan/suppressions.txt	(revision 64921)
+++ tools/valgrind/tsan/suppressions.txt	(working copy)
@@ -147,7 +147,7 @@
 }
 
 {
-  bug_61585
+  bug_61585a
   ThreadSanitizer:UnlockForeign
   fun:pthread_mutex_destroy
   ...
@@ -157,6 +157,18 @@
 }
 
 {
+  bug_61585b
+  ThreadSanitizer:UnlockNonLocked
+  fun:pthread_mutex_unlock
+  fun:PR_Unlock
+  fun:nssSession_ExitMonitor
+  fun:find_objects
+  ...
+  fun:nssTrustDomain_FindCertificatesBySubject
+  ...
+}
+
+{
   bug_61753
   ThreadSanitizer:Race
   ...