libc: Avoid SIGPIPE when nscd closes the connection unexpectedly.

It is almost always a bug if nscd closes the connection unexpectedly but
programs should not be killed with SIGPIPE for it.

Reviewed by:	bushman
Tested by:	Jan Beich
MFC after:	1 week
Add missed `_load' to the `if_foo_load="YES"' line.

PR:		docs/176915
MFC after:	1 week