gendispatch: Avoid comparing signed and unsigned vars

gendispatch: Avoid comparing signed and unsigned vars

The adminDispatchConnectListServers() function is generated by
our great perl script. However, it has a tiny flaw: if
adminConnectListServers() it calls fails, the control jumps onto
cleanup label where we try to free any list of servers built so
far. However, in the loop @i is unsigned (size_t) while @nresults
is signed (int). Currently, it does no harm because of the check
for @result being non-NULL. But if that ever changes in the
future, this bug will be hard to chase.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>