Add missing post create and alter hooks to policy objects.
Add missing post create and alter hooks to policy objects.

AlterPolicy() and CreatePolicy() lacked their respective hook invocations.
Noted by Noah Misch, review by Dean Rasheed. Back-patch to 9.5 where
RLS was introduced.

zeroae/postgres-xl,zeroae/postgres-xl,zeroae/postgres-xl,zeroae/postgres-xl,zeroae/postgres-xl