by default hosts shall be not found

by default hosts shall be not found

otherwise, if a default constructed QHostInfo object is emited from thread
used to lookup it will be considered as sucessfull lookup (i.e. the error
is QHostInfo::NoError), even if the host is found it may be unreachable
right after the lookup is done (e.g. lookup before fetch, lookup succeeded,
server crashes before fetching data from it - server is unreachable). in
other words - it's a stat() before open() like problem

Signed-off-by: Ivailo Monev <xakepa10@gmail.com>