s3:passdb: Fix memory leak in pdb_default_add_groupmem()

s3:passdb: Fix memory leak in pdb_default_add_groupmem()

Indirect leak of 496 byte(s) in 1 object(s) allocated from:
    #0 0x7f068f921c2b in malloc (/lib64/libasan.so.8+0x121c2b) (BuildId: 388ee9ac193f74c177c6f52988d2d0dab110de41)
    #1 0x7f068f4266a0 in __talloc_with_prefix ../../lib/talloc/talloc.c:783
    #2 0x7f068f427f75 in __talloc ../../lib/talloc/talloc.c:825
    #3 0x7f068f427f75 in _talloc_named_const ../../lib/talloc/talloc.c:982
    #4 0x7f068f427f75 in _talloc_zero ../../lib/talloc/talloc.c:2421
    #5 0x7f068cbba260 in samu_new ../../source3/passdb/passdb.c:63
    #6 0x7f068cbda444 in pdb_default_add_groupmem ../../source3/passdb/pdb_interface.c:1022
    #7 0x7f068cbd825d in pdb_add_groupmem ../../source3/passdb/pdb_interface.c:1054
    #8 0x000000389322 in net_sam_addmem ../../source3/utils/net_sam.c:1255
    #9 0x00000038ff79 in net_run_function ../../source3/utils/net_util.c:451
    #10 0x00000038bfb6 in net_sam ../../source3/utils/net_sam.c:2306
    #11 0x00000038ff79 in net_run_function ../../source3/utils/net_util.c:451
    #12 0x0000002ea182 in main ../../source3/utils/net.c:1474
    #13 0x7f068a42b2fa in __libc_start_call_main (/lib64/libc.so.6+0x2b2fa) (BuildId: 8523b213e7586a93ab00f6dd476418b1e521e62c)
    #14 0x7ffe0a90b7a1  ([stack]+0x207a1)

Signed-off-by: Andreas Schneider <asn@samba.org>
Reviewed-by: Anoop C S <anoopcs@samba.org>