Lock around access to nc_file and netconfig_info ("ni").  The RPC part of libc is still not thread safe but this would at least reduce the problems we have.
Lock around access to nc_file and netconfig_info ("ni").  The RPC
part of libc is still not thread safe but this would at least
reduce the problems we have.

PR:		threads/118544
Submitted by:	Changming Sun <snnn119 gmail com>
MFC after:	2 weeks

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