Revert r300385 and r300624 which was false positive
reported by cppcheck.

dup_ncp() tries to allocate a buffer of MAXNETCONFIGLINE
as tmp, which is then assigned to p->nc_netid via strcpy,
so the free(p->nc_netid) would have correctly released
the memory in case nc_lookups() fails, therefore, the
allerged leak never existed.

MFC after: 3 days