debuginfod-client.c: Skip negative cache entry for cancelled downloads

debuginfod-client.c: Skip negative cache entry for cancelled downloads

The debuginfod client cache uses empty files to indicate that a download
was unsuccessful and should not be attempted again.

Commit 5527216460c61 skips the creation of empty files when a downloaded
is cancelled by the user.  This works by setting
client->progressfn_cancel to true when progressfn returns a non-zero value.

Commit d47d93b1049ec appears to have accidentally removed this setting of
client->progressfn_cancel.

Restore setting client->progressfn_cancel to true when progressfn
returns a non-zero value.  Also set client->progressfn_cancel to false
at the beginning of debuginfod_find_metadata to avoid previous
cancellations affecting the current metadata query.

Signed-off-by: Aaron Merey <amerey@redhat.com>