EX-3636 pcc: set invalid cache state for fallback I/O

EX-3636 pcc: set invalid cache state for fallback I/O

When fallback I/O to Lustre (not PCC backend), it should set the
cache state correctly (with *cached = false).

Fixes: c3cf63c830 ("EX-3636 pcc: reset file mmaping for the file once mmaped")
Signed-off-by: Qian Yingjin <qian@ddn.com>
Change-Id: I4e7dad93c589ac8062fe6c08423bf209f08432b6
Reviewed-on: https://review.whamcloud.com/44793
Reviewed-by: Yang Sheng <ys@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>