OS-251 add the pkt_reason field to the slow-io error detector
Reviewed by: Hans Rosenfeld <hans.rosenfeld@nexenta.com>
Reviewed by: Albert Lee <albert.lee@nexenta.com>
Reviewed by: Michael Tsymbalyuk <michael.tsymbalyuk@nexenta.com>
Revert "OS-6 mpathadm leads to panic in vhci_mpapi_sync_lu_oid_list"

This reverts commit 6071cd0aa829ffad7d7e9e09ee6c6e7da1344530.
OS-253 we should not free mdi_pathinfo_t in mptsas when device(s) are retired
NEX-1923 Retiring a device may hang or have leave device unusable after unretire
NEX-1438 bump slow-io threshold and default to disabled automated response