backport: core: fix network faults handling and fencing flow

[mwperina]

This patch fixes network exception handling and fencing flow logic.
Problems in current code:

1. Hard fencing happens too fast since we waited on number of

attempts grace period, since number of attempts is configured to a
value of "2", grace period was ~20 seconds.

2. VdsManager::isHostInGracePeriod was called periodically from

VdsManager:handleNetworkExeception and from
SsshSoftFencingCommand::checkIfHostBecomeUp which makes the logic
complex in not working as expected
While we have to handle the network exception grace period when the host
is switched to 'connecting' state due to its load regarding number of
running VMs and SPM status, in the case of soft-fencing flow, the host
is already in not-responding status, other host already took the SPM
role and all its running VMs set to 'unknown' status. So we should not
consider the host load at all and a fixed grace period (configurable 1
min) is enough to restart the vdsmd service on the host and get it up
and running.

Solution was tested with host as SPM with running VMs (some are HA),
with a non SPM host running VMs and with a regular host.

Results:

1. Both initial grace between connecting and non-responding and between
   soft-fencing and hard-fencing are honored.

2. Code is more readable and straight foreword

Signed-off-by: Eli Mesika emesika@redhat.com
Bug-Url: https://bugzilla.redhat.com/2071468

[mwperina]

Verified on master