MFC r255043 (by ken):
Bump up the default timeouts for move commands in the ch(4) driver
to 15 minutes, and 5 minutes for things like READ ELEMENT STATUS.

This is needed to account for the worst case scenarios on at least
some Spectra Logic tape libraries.
MFC r256547 (by smh):
Added 4K quirks for Corsair Neutron GTX SSD's
MFC r257946:
Introduce seperate mutex lock to protect protect CTL I/O pools, slightly
reducing global CTL lock scope and congestion.

While there, simplify CTL I/O pools KPI, hiding implementation details.
MFC r258871:
Properly report an error instead of panicing when user tries to create
LUN backed by non-disk device, e.g. /dev/null.
MFC r262782 (by trasz):
Fix missing unlock in persistent reservations code, which resulted in panics
with Hyper-V Failover Cluster.