light: enable logfile fetch debugging
light: fix logfile fetch after leave-resource && join-resource
marsadm: remove superfluous connect links
marsadm: prevent mutual overwrite of delete symlinks

Add an (unused) host context. Previously, concurrent
log-delete operations triggered by cron could lead to
unnecessary loss of deletetion symlinks.
light: prevent races between deletions and re-erected objects
marsadm: wait for deletions after leave-resource
marsadm: reject invalidate earlier when no primary is designated
marsadm: do resource checks only once per command
marsadm: early abort is-device-on when not designated primary
marsadm: print warnings when SPLIT BRAIN is detected
marsadm: disallow 'primary --force' in connected state

DRBD does not allow to deliberately provoke a SPLIT BRAIN
in connected state.

Thus MARS Light cannot be required to support such silly things
in any way.
marsadm: allow overrides of "marsadm secondary" in disconnected clusters

When the communication is down in partitioned clusters, the command
"marsadm seconodary" would normally use the current timestamp of
the command execution for the Lamport update protocol.

Make an exception for the case that a concurrent "marsadm primary"
was given somewhere else on a disconnected / partitioned node: let
the "primary" always win over a "secondary" command.
marsadm: wait for devices to {dis,}appear even on {prim,second}ary --force
marsadm: better error message at failed 'invalidate'
light: prevent logfile fetching on primaries and behind split brains

Save space in /mars/ by not fetching useless logfiles.
marsadm: reject join-resource if no primary is designated
marsadm: remove all version links at leave-resource
marsadm: fix faking new versionlink on join-resource
marsadm: fix version links in 'invalidate'
marsadm: always update timestamp of primary symlink