CA-128460: Don't pause tapdisk in the toolstack

This only affects the storage migration code path.

We were pausing in order to flush all pending requests before
checking to see if any of them failed to mirror correctly. Now
tapdisk has exposed a 'reqs_outstanding' counter. We loop
waiting for this to go to zero, then check the
'nbd_mirror_failed' flag.

Signed-off-by: Jon Ludlam <jonathan.ludlam@citrix.com>
Log session stats every 10 mins

Signed-off-by: Jon Ludlam <jonathan.ludlam@citrix.com>
Increase the session limit

Signed-off-by: Jon Ludlam <jonathan.ludlam@citrix.com>
Remove 4 spammy log lines

Signed-off-by: Jon Ludlam <jonathan.ludlam@citrix.com>
CA-147261: Add average queue size metric for tapdisk3

Prior to this patch, the average queue size metric was missing.
This patch computes this metric using the stats exposed by tapdisk3.
Average queue size is defined as the sum of the average read and write queues.

Signed-off-by: Siddharth Vinothkumar <siddharth.vinothkumar@citrix.com>
Merge pull request #1966 from jonludlam/creedence-log-bits-and-bobs

Creedence log bits and bobs
Merge pull request #1965 from siddharthv/CA-147261

CA-147261: Add average queue size metric for tapdisk3
Use Oclock rather than Unix.time for deltas

Signed-off-by: Jon Ludlam <jonathan.ludlam@citrix.com>
Merge pull request #1967 from jonludlam/CA-128460-creedence

CA-128460: Don't pause tapdisk in the toolstack
CA-147786: Export VDI snapshot_of links

Signed-off-by: John Else <john.else@citrix.com>
Logging change

Signed-off-by: John Else <john.else@citrix.com>
Refactor Import.update_snapshot_and_parent_links

Signed-off-by: John Else <john.else@citrix.com>
CA-147786: Update snapshot_of links for imported VDIs

Signed-off-by: John Else <john.else@citrix.com>
Update snapshots map after the cross-pool metadata transfer (if any)

Signed-off-by: John Else <john.else@citrix.com>