ctdb-daemon: Fix maybe-uninitialized error with picky developer

ctdb-daemon: Fix maybe-uninitialized error with picky developer

263/386] Compiling ctdb/server/ctdb_recovery_helper.c
In file included from ../../server/ctdb_recovery_helper.c:24:0:
../../server/ctdb_recovery_helper.c: In function ‘main’:
../../../lib/talloc/talloc.h:911:34: error: ‘mem_ctx’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
 #define TALLOC_FREE(ctx) do { if (ctx != NULL) { talloc_free(ctx); ctx=NULL; } } while(0)

Signed-off-by: Amitay Isaacs <amitay@gmail.com>
Reviewed-by: Jeremy Allison <jra@samba.org>