MB-15348 Remove unused spinlock from file buffer cache structure.
MB-15348 Remove unused spinlock from file buffer cache structure.

Change-Id: I20c2b528f28c89ccc1832f396bd57b1a24dd1ee4

hisundar/forestdb,wurikiji/forestdb,joliss/forestdb,couchbase/forestdb,yyangpan/forestdb,couchbase/forestdb,wurikiji/forestdb,sushmaad/forestdb,jinxuan/forestdb,joliss/forestdb,jinxuan/forestdb,zhaog/forestdb,zhaog/forestdb,yyangpan/forestdb,sushmaad/forestdb,hisundar/forestdb