Description of problem:
When running reproducer for bug 769616, valgrind reports a memory leak.

Version-Release number of selected component (if applicable):
nss-3.15.1-3.el6.s390x

How reproducible:
Always

Steps to Reproduce:
  cat <<EOF > ckfw_leaks_memory.c
#include <assert.h>
#include <nss.h>
#include <secmod.h>
#include <stdlib.h>

int main() {
  if (0 != NSS_NoDB_Init(NULL))
    assert(0);

  for (int i = 0; i < 256; ++i) {
    SECMODModule* mod = SECMOD_LoadUserModule("library=libnsspem.so name=PEM", NULL, PR_FALSE);
    if(!mod || !mod->loaded)
      assert(0);

    SECMOD_UnloadUserModule(mod);
    SECMOD_DestroyModule(mod);
  }

  NSS_Shutdown();

  return EXIT_SUCCESS;
}
EOF
gcc ckfw_leaks_memory.c -o ckfw_leaks_memory -g -std=c99 -pedantic -W -Wall -I/usr/include/nss3 -I/usr/include/nspr4 -lnss3
LD_PRELOAD=libnsspem.so valgrind --leak-check=full --error-exitcode=7 ./ckfw_leaks_memory

Actual results:
==15960== Memcheck, a memory error detector
==15960== Copyright (C) 2002-2012, and GNU GPL'd, by Julian Seward et al.
==15960== Using Valgrind-3.8.1 and LibVEX; rerun with -h for copyright info
==15960== Command: ./ckfw_leaks_memory
==15960== 
==15960== 
==15960== HEAP SUMMARY:
==15960==     in use at exit: 10,585 bytes in 89 blocks
==15960==   total heap usage: 83,922 allocs, 83,833 frees, 35,332,256 bytes allocated
==15960== 
==15960== 272 bytes in 1 blocks are definitely lost in loss record 68 of 75
==15960==    at 0x402BA84: calloc (vg_replace_malloc.c:593)
==15960==    by 0x43ADCB3: _PR_InitThreads (ptthread.c:939)
==15960==    by 0x439D517: _PR_InitStuff (prinit.c:180)
==15960==    by 0x439D7AD: PR_CallOnce (prinit.c:219)
==15960==    by 0x408E9C9: nss_Init (nssinit.c:548)
==15960==    by 0x408F943: NSS_NoDB_Init (nssinit.c:874)
==15960==    by 0x800008DD: main (ckfw_leaks_memory.c:7)
==15960== 
==15960== LEAK SUMMARY:
==15960==    definitely lost: 272 bytes in 1 blocks
==15960==    indirectly lost: 0 bytes in 0 blocks
==15960==      possibly lost: 0 bytes in 0 blocks
==15960==    still reachable: 10,313 bytes in 88 blocks
==15960==         suppressed: 0 bytes in 0 blocks
==15960== Reachable blocks (those to which a pointer was found) are not shown.
==15960== To see them, rerun with: --leak-check=full --show-reachable=yes
==15960== 
==15960== For counts of detected and suppressed errors, rerun with: -v
==15960== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 264 from 8)

Expected results:
No memory leaks

Additional info:
This bug might have been introduced by errata 12964, but couldn't be detected because of bug 823005 and issues described in bug 700359. This is NOT a regresion from 6.4.z.