MEMCACHEGlobals doesn't need to be RequestLocal

Summary: Ini settings are auto-reset to their default values
at the end of every request anyway.

Also fixes a bug where the setter for hash_function set
hash_strategy by mistake

Reviewed By: @ptarjan

Differential Revision: D1625606
SessionRequestData shouldn't be RequestLocal

Summary: Its always initialized at the start of every request,
so the lazy initialization is just pointless overhead; and its
shutdown has to be handled specially anyway.

Reviewed By: @ptarjan

Differential Revision: D1625631
Unrevert "Revert various HNI conversions"

Summary: This reverts commit 9073b64e3a15293308c9034143d6d63bd6a7988b (D1601800). Since D1414528 landed, these changes should be safe to unrevert.

Reviewed By: @markw65

Differential Revision: D1614465