block/curl: Improve type safety of s->timeout.

qemu_opt_get_number returns a uint64_t, and curl_easy_setopt expects a
long (not an int).

Store the timeout (which is a positive number of seconds) as a
uint64_t.  Check that the number given by the user is reasonable.
Cast it to long before calling curl_easy_setopt.

Example error message after this change has been applied:

$ ./qemu-img create -f qcow2 /tmp/test.qcow2 \
    -b 'json: { "file.driver":"https",
                "file.url":"https://foo/bar",
                "file.timeout":-1 }'
qemu-img: /tmp/test.qcow2: Could not open 'json: { "file.driver":"https", "file.url":"https://foo/bar", "file.timeout":-1 }': timeout parameter is too large or negative: Invalid argument

Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Message-id: 1412605930-3397-1-git-send-email-rjones@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
snapshot: Reset err to NULL to avoid double free

If an error occurs in bdrv_snapshot_delete_by_id_or_name(), "err" is
freed.  If "err" is not set to NULL before calling
bdrv_snapshot_delete_by_id_or_name() again, it will not be updated on
error, and will be freed again.

This can be triggered by starting a VM with at least two drives and then
attempting to delete a non-existent snapshot.

Broken in commit a89d89d.

Signed-off-by: Chris Spiegel <chris.spiegel@cypherpath.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-id: 1412613225-32676-1-git-send-email-chris.spiegel@cypherpath.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>