library: address an 'uninitialised value' VALGRIND bug

Thanks to valgrind and his --track-origins=yes option,
the problem and solution was suggested as shown below.

[ and it was created in that commit referenced below ]

But, after attacking this problem by adding a memset()
call in pids.c, a 2nd valgrind oops, also shown below,
was encountered. The dynamically acquired 'cmd' again!

[ might help to explain why changes appear excessive ]

Reference(s):
. 1st valgrind discovery
==11111== Conditional jump or move depends on uninitialised value(s)
==11111==    at 0x13425D: stat2proc (readproc.c:582)
==11111==    by 0x137436: look_up_our_self (readproc.c:1613)
==11111==    by 0x132196: fatal_proc_unmounted (pids.c:1388)
==11111==    by 0x11BA4D: before (top.c:3580)
==11111==    by 0x127E10: main (top.c:7173)
==11111==  Uninitialised value was created by a stack allocation
==11111==    at 0x132165: fatal_proc_unmounted (pids.c:1381)

. Jul, 2022 - fatal_proc_unmounted refactored
commit 52bd019d8c

. 2nd valgrind discovery
==22222== 16 bytes in 1 blocks are definitely lost
==22222==    by 0x4A0E60E: strdup (strdup.c:42)
==22222==    by 0x133D00: stat2proc (readproc.c:587)
==22222==    by 0x136E67: look_up_our_self (readproc.c:1613)
==22222==    by 0x131BC7: fatal_proc_unmounted (pids.c:1390)
==22222==    by 0x11B7C6: before (top.c:3580)
==22222==    by 0x127828: main (top.c:7173)

Signed-off-by: Jim Warner <james.warner@comcast.net>

library/pids.c

@@ -1381,11 +1381,10 @@ PROCPS_EXPORT struct pids_stack *fatal_proc_unmounted (
 {
     struct pids_fetch *fetched;
     unsigned tid;
-    proc_t self;
 
     /* this is very likely the *only* newlib function where the
        context (pids_info) of NULL will ever be permitted */
-    if (!look_up_our_self(&self)
+    if (!look_up_our_self()
     || (!return_self))
         return NULL;