LU-10994 clio: remove cl_page_export() and cl_page_is_vmlocked()

LU-10994 clio: remove cl_page_export() and cl_page_is_vmlocked()

Remove cl_page_export() and cl_page_is_vmlocked(), replacing them with
direct calls to PageSetUptodate() and PageLoecked().

Signed-off-by: John L. Hammond <jhammond@whamcloud.com>
Change-Id: I883d1664f4afc7a1d4006f9f4833db8125c0e8f5
Reviewed-on: https://review.whamcloud.com/47241
Reviewed-by: Patrick Farrell <pfarrell@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Oleg Drokin <green@whamcloud.com>