getdata: increase max number of shared networks

getdata: increase max number of shared networks

Anders & Thor Eivind reported dhcpd-pools to mess console and
crash at the end of execution. Reason was missing boundary check.
The fix this time is more of less just a increase to max numbers.
That will work ot some extent.

The memory allocations has to be made fully dynamic, but that is
a little bit difficult with the way default.h and parse_config
are working. Basically problem is globals gone crazy & re-entrant
issue with parse function. The true fix to the issue will have to
wait for complete redesign of internals of the command.

Reported-by: Anders Låstad <ala@nextgentel.com>
Reported-by: Thor Eivind Brantzeg <tbr@nextgentel.com>
Signed-off-by: Sami Kerola <kerolasa@iki.fi>