Redirect /var/run/nscd/socket to ENOENT to disable NSCD.

Name Service Cache Daemon (NSCD) is installed in CSE workstations for
passwd, group services, which does not check /etc/passwd and /etc/group.
parrot_identity_box is based on adding items into /etc/passwd and /etc/group.
Merge pull request #577 from hmeng-19/parrot_identity_box

Disable NSCD when using parrot_identity_box