widen leak supression.  looks like start_keepalive is sometimes inlined.

BUG=skia:

Review URL: https://codereview.chromium.org/1008873003
diff --git a/tools/valgrind.supp b/tools/valgrind.supp
index 28429c0..ffb7108 100644
--- a/tools/valgrind.supp
+++ b/tools/valgrind.supp
@@ -7,7 +7,7 @@
    match-leak-kinds: possible
    ...
    fun:_ZN8SkThreadC1EPFvPvES0_
-   fun:_ZL15start_keepalivev
+   ...
    fun:_Z7dm_mainv
    fun:main
 }