[pve-devel] Add predelay to startup order of startall VMs

[Thomas Lamprecht]

In addition to 'up', 'down' add 'predelay' which is a delay executet before
we try to start a VM. Its main reason is to give the First starting VM(s) a
delay, this was often wished in the forum/userlist and had also valid reasons,
e.g. ceph was not quite ready, or rebalances still and someone does not want to
give then ceph additional load, also iSCSI had problems, see the forum thread
linked in the commit messages.

This is an RFC, option name is up to discussion, implementaion is quite
straight forward, I used a similar on as for the 'up' delay.

If this idea gets accessed I also make a Patch for the GUI so that it can
at least show the setting if wanted.