Race conditions in getnetconfig

Race conditions in getnetconfig

The clnt_* functions are *not* thread safe. Race conditions are caused
by the functions setnetconfig , getnetconfig, endnetconfig and
getnetconfigent that accesses global static data nc_file and ni which
are defined in the file getnetconfig are *not* protected by any mutex.
When more than one thread access them the variables become a nonlocal
side effect . These race conditions causing process to give undesired
behavior and leading to crash on file operations mostly on fclose. By
introducing the mutex nc_db_lock the netconfig database is synchronized
and prevented from crash.

Signed-off-by: Susant Sahani <ssahani@redhat.com>
Signed-off-by: Steve Dickson <steved@redhat.com>