Add support for flashing image to correct slot locally

This commit modifies the aboot-deploy script to add support for flashing the image to the correct slot using the -l/--local flag. Additionally, it introduces documentation for the -o/--options flag to specify the cmdline of the next boot, used by OSTree. With these changes, users can now flash the image to the correct slot for rpm kernel upgrades.

This can be run via:

aboot-deploy -l aboot-$(uname -r).img

We intend on adding this step to kernel upgrade script in aboot-update package so that on an rpm install and reboot your new kernel upgrade is booted.

Signed-off-by: Eric Curtin ecurtin@redhat.com