tools: suppress some reachable external lib "leaks"

- These are just normal reachable allocs from inside external library code;
however, when running valgrind with memleak types "all" in order to find FRR
specific leaks (from memory.h) these are the only other reported leaks. Makes
easier checking and fixing.

Signed-off-by: Christian Hopps <chopps@labn.net>

tools/valgrind.supp

@@ -23,6 +23,15 @@
    fun:cap_init
    fun:zprivs_caps_init
 }
+{
+   <zprivs_init leak in library code we do not control>
+   Memcheck:Leak
+   match-leak-kinds: reachable
+   ...
+   fun:getgrouplist
+   fun:zprivs_init
+   fun:frr_init
+}
 {
    <sqlite3 leak in a function we do not control>
    Memcheck:Leak