Only set delayed inval for procs using PTI

[vangyzen]

Summary

invltlb_invpcid_pti_handler() was requesting delayed TLB invalidation
even for processes that aren't using PTI. With an out-of-tree
change to avoid PTI for non-jailed root processes, this caused an
assertion failure in pmap_activate_sw_pcid_pti() when context-switching
between PTI and non-PTI processes.

Sponsored by: Dell EMC Isilon

Test Plan

With that out-of-tree change, systems using PTI always panic during boot,
soon after the first non-root process is started. With the fix, they boot.