Ensure handle always has correct last_hdr_bid & cur_header_revnum
Ensure handle always has correct last_hdr_bid & cur_header_revnum

- Since header data is read after getting revnum & header BID, handle
might have the previous version of those numbers compared to the
header data.

- We need to synchronize all those data at the time that
filemgr_get_header() is called.

Change-Id: Ieec3a3846d9b1f18a136ad598be196e198667da4

couchbase/forestdb,wurikiji/forestdb,couchbase/forestdb,hisundar/forestdb,hisundar/forestdb,wurikiji/forestdb