Ticket 48920 - Memory leak in pwdhash-bin

Bug Description:  We have a memory leak in pwdhash-bin

    ==388==ERROR: LeakSanitizer: detected memory leaks

    Direct leak of 72 byte(s) in 1 object(s) allocated from:
        #0 0x7f5f5f94dfd0 in calloc (/lib64/libasan.so.3+0xc6fd0)
        #1 0x7f5f5d7f72ae  (/lib64/libnss3.so+0x752ae)

    SUMMARY: AddressSanitizer: 72 byte(s) leaked in 1 allocation(s).

Fix Description:  Properly shutdown NSS at the end of usage

https://fedorahosted.org/389/ticket/48920

Author: wibrown

Review by: nhosoi

ldap/servers/slapd/tools/pwenc.c

@@ -263,6 +263,9 @@ main( argc, argv )
 
 	plugin_closeall( 1 /* Close Backends */, 1 /* Close Globals */);
 
+    /* Shutdown NSS to free values */
+    (void)NSS_Shutdown();
+
 	return( rc == 0 ? 0 : 1 );
 }