clamav: Allow downloads to take up to 10 minutes

clamav: Allow downloads to take up to 10 minutes

freshclam did not have a receive timeout set and a default of
60s was used. That causes that the large main database cannot
be downloaded over a line with a 16 MBit/s downlink.

This patch increases that timeout and should allow a successful
download on slower connections, too.

Suggested-by: Tim Fitzgeorge <ipfb@tfitzgeorge.me.uk>
Fixes: #12246
Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>
Reviewed-by: Peter Müller <peter.mueller@ipfire.org>
Signed-off-by: Arne Fitzenreiter <arne_f@ipfire.org>