pf: Fix table entry counter toggling

[markj]

Summary

When updating a table, pf will keep table entry structures corresponding
to addresses that are in both of the old and new tables. However, the
update may also enable or disable per-entry counters which are allocated
separately. Thus when toggling PFR_TFLAG_COUNTERS, the entries may be
missing counters or may have unused counters allocated.

Fix the problem by modifying pfr_ina_commit() to transfer counters
from or to the shadow table.

Reported by: [e-mail]

Test Plan

Regression tests pass. I will write a test case for this if the code change seems ok.