mstor_do_chunkfind: fix some bugs
mstor_do_chunkfind: fix some bugs

* check read permission on the file itself, not its parent directory,
before fetching chunk information.

* get rid of unused 'err' variable.

Signed-off-by: Colin McCabe <3142ce8a0bdba4a38073365893e6b74f72d9c512@alumni.cmu.edu>

cmccabe/redfish,cmccabe/redfish,cmccabe/redfish,cmccabe/redfish,cmccabe/redfish