Changes

Revert "s1gw: cache PFCP Recovery Timestamp in ConnHdlr"

This reverts commit 7ad95e1cfb00d269069bd052c44a9cae9027f763.

A follow-up commit will remove the need for each ConnHdlr to call
f_ConnHdlr_register_pfcp(), that among with handling the PFCP
association retrieves a PFCP Recovery Timestamp from the PFCPEM.

Caching the PFCP Recovery Timestamp value is not really worth it,
since it's rarely used and can always be retrieved on demand.

Change-Id: I3b1c488e3ec251c7659cd9bc3197cca2f9d03144