xenstore: handle daemon creation errors

xenstore: handle daemon creation errors

In rare cases, the path to the daemon socket cannot be created as it is
longer than PATH_MAX. Instead of failing with a NULL pointer dereference,
terminate the application with an error message.

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

Signed-off-by: Norbert Manthey <nmanthey@amazon.de>
Reviewed-by: Thomas Friebel <friebelt@amazon.de>
Reviewed-by: Julien Grall <jgrall@amazon.co.uk>
Reviewed-by: Juergen Gross <jgross@suse.com>