tools/xenstored: Avoid unnecessary talloc_strdup() in do_lu_start()

At the moment, the return of talloc_strdup() is not checked. This means
we may dereference a NULL pointer if the allocation failed.

However, it is pointless to allocate the memory as send_reply() will
copy the data to a different buffer. So drop the use of talloc_strdup().

This bug was discovered and resolved using Coverity Static Analysis
Security Testing (SAST) by Synopsys, Inc.

Fixes: af216a99fb ("tools/xenstore: add the basic framework for doing the live update")
Signed-off-by: Julien Grall <jgrall@amazon.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Release-Acked-by: Ian Jackson <iwj@xenproject.org>

tools/xenstore/xenstored_control.c

@@ -638,7 +638,6 @@ static bool do_lu_start(struct delayed_request *req)
 {
 	time_t now = time(NULL);
 	const char *ret;
-	char *resp;
 
 	if (!lu_check_lu_allowed()) {
 		if (now < lu_status->started_at + lu_status->timeout)
@@ -660,8 +659,7 @@ static bool do_lu_start(struct delayed_request *req)
  out:
 	talloc_free(lu_status);
 
-	resp = talloc_strdup(req->in, ret);
-	send_reply(lu_status->conn, XS_CONTROL, resp, strlen(resp) + 1);
+	send_reply(lu_status->conn, XS_CONTROL, ret, strlen(ret) + 1);
 
 	return true;
 }