qemu-img: Fix insignificant memleak

As soon as options is set in img_amend(), it needs to be freed before
the function returns. This leak is rather insignificant, as qemu-img
will exit subsequently anyway, but there's no point in not fixing it.

Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Benoit Canet <benoit@irqsave.net>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Benoît Canet <benoit.canet@nodalink.com>
Message-id: 1414404776-4919-4-git-send-email-mreitz@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
