api/backup: handle new vzdump jobs

api/backup: handle new vzdump jobs

in addition to listing the vzdump.cron jobs, also list from the
jobs.cfg file.

updates/creations go into the new jobs.cfg only now
and on update, starttime+dow get converted to a schedule
this transformation is straight forward, since 'dow'
is already in a compatible format (e.g. 'mon,tue') and we simply
append the starttime (if any)

id on creation is optional for now (for api compat), but will
be autogenerated (uuid). on update, we simply take the id from before
(the ids of the other entries in vzdump.cron will change but they would
anyway)

as long as we have the vzdump.cron file, we must lock both
vzdump.cron and jobs.cfg, since we often update both

we also change the backupinfo api call to read the jobs.cfg too

Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>