CA-128460: Don't pause tapdisk in the toolstack
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 <e7e3380887a8f95cc9dc4f0d51dedc7e849a287a@citrix.com>
(cherry picked from commit 02a1474cffc20a25fbb72357f4d99c83dd3d58e3)

simonjbeaumont/xen-api,vasilenkomike/xen-api,cheng-z/xen-api,cheng--zhang/xen-api,guard163/xen-api,koushikcgit/xen-api,cheng-z/xen-api,thomassa/xen-api,koushikcgit/xen-api,simonjbeaumont/xen-api,anoobs/xen-api,euanh/xen-api,srowe/xen-api,salvocambria/xen-api,guard163/xen-api,vasilenkomike/xen-api,cheng-z/xen-api,jjd27/xen-api,anoobs/xen-api,rafalmiel/xen-api,thomassa/xen-api,guard163/xen-api,srowe/xen-api,Frezzle/xen-api,anoobs/xen-api,jjd27/xen-api,vasilenkomike/xen-api,jjd27/xen-api,rafalmiel/xen-api,srowe/xen-api,srowe/xen-api,robertbreker/xen-api,Frezzle/xen-api,euanh/xen-api,euanh/xen-api,salvocambria/xen-api,guard163/xen-api,koushikcgit/xen-api,euanh/xen-api,simonjbeaumont/xen-api,salvocambria/xen-api,agimofcarmen/xen-api,guard163/xen-api,vasilenkomike/xen-api,Frezzle/xen-api,cheng--zhang/xen-api,agimofcarmen/xen-api,djs55/xen-api,agimofcarmen/xen-api,thomassa/xen-api,djs55/xen-api,djs55/xen-api,robertbreker/xen-api,thomassa/xen-api,djs55/xen-api,Frezzle/xen-api,jjd27/xen-api,agimofcarmen/xen-api,rafalmiel/xen-api,agimofcarmen/xen-api,agimofcarmen/xen-api,koushikcgit/xen-api,guard163/xen-api,robertbreker/xen-api,anoobs/xen-api,simonjbeaumont/xen-api,anoobs/xen-api,koushikcgit/xen-api,salvocambria/xen-api,simonjbeaumont/xen-api,cheng--zhang/xen-api,cheng--zhang/xen-api,koushikcgit/xen-api,cheng--zhang/xen-api,Frezzle/xen-api,cheng-z/xen-api,cheng-z/xen-api,cheng--zhang/xen-api,robertbreker/xen-api,thomassa/xen-api,cheng-z/xen-api,jjd27/xen-api,srowe/xen-api,euanh/xen-api,rafalmiel/xen-api,cheng-z/xen-api,vasilenkomike/xen-api,thomassa/xen-api,simonjbeaumont/xen-api,anoobs/xen-api,rafalmiel/xen-api,cheng--zhang/xen-api,salvocambria/xen-api,euanh/xen-api,jjd27/xen-api,robertbreker/xen-api,djs55/xen-api,vasilenkomike/xen-api,djs55/xen-api,rafalmiel/xen-api,robertbreker/xen-api,salvocambria/xen-api