loadparm: fix mem leak found by ASAN

loadparm: fix mem leak found by ASAN

==24948==ERROR: LeakSanitizer: detected memory leaks

Indirect leak of 232 byte(s) in 1 object(s) allocated from:
    #0 0x7fc44b971c08 in __interceptor_malloc (/lib64/libasan.so.5+0xefc08)
    #1 0x7fc44a2fe7b0 in __talloc_with_prefix ../../lib/talloc/talloc.c:782
    #2 0x7fc44a2fe7b0 in __talloc ../../lib/talloc/talloc.c:824
    #3 0x7fc44a2fe7b0 in _talloc_named_const ../../lib/talloc/talloc.c:981
    #4 0x7fc44a2fe7b0 in _talloc_array ../../lib/talloc/talloc.c:2764
    #5 0x7fc44a1239bc in str_list_make_v3 ../../lib/util/util_strlist_v3.c:58
    #6 0x7fc44a123e3b in str_list_make_v3_const ../../lib/util/util_strlist_v3.c:127
    #7 0x7fc44b14cc1a in init_globals ../../source3/param/loadparm.c:547
    #8 0x7fc44b14deef in lp_load_ex ../../source3/param/loadparm.c:3876
    #9 0x7fc44b14f97c in lp_load_initial_only ../../source3/param/loadparm.c:4025
    #10 0x7fc44b479235 in cmdline_messaging_context ../../source3/lib/cmdline_contexts.c:34
    #11 0x557cf59d642c in process_options ../../source3/utils/smbpasswd.c:200
    #12 0x557cf59d642c in main ../../source3/utils/smbpasswd.c:633
    #13 0x7fc4419f5412 in __libc_start_main (/lib64/libc.so.6+0x24412)

Signed-off-by: Swen Schillig <swen@linux.ibm.com>
Reviewed-by: Matthias Dieter Wallnöfer <mdw@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>
Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Sat Aug 10 20:42:39 UTC 2019 on sn-devel-184