nfsdcltrack: break out a function to open the database handle

When we add a new usermodehelper upcall program to do the database
access, the existing "init" function will be overkill every time
we start up the program.

Break out the database handle establishment routine into a separate
function that we can call from each upcall command in the one-shot
program.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve Dickson <steved@redhat.com>