linux-cp: detect and delete stale entries after sync

linux-cp: detect and delete stale entries after sync

Type: improvement

During synchronization, only the current actual set of entries is
loaded. If some entries are no longer present in the set being loaded
but present in VPP, they should be removed to fully syncronize.

With this change, add handlers for sync begin and end events. Begin
handlers will mark the entries as stale. End handlers will remove the
entries that are still marked as stale.

Signed-off-by: Alexander Chernavin <[email protected]>
Change-Id: I4f7e872af3e1c9ffa6c63bcc3984ec76def1bb43