Linux: Rework statfs super block operations configure test

Linux: Rework statfs super block operations configure test

The configure test to detect if the statfs super block operation
needs a dentry argument is based on vfs_statfs, and assumes that
its signature matches the one of the operation.  In 2.6.36 this is
no longer true and the test fails.

Rework the test to actually test the operation we're interested in.

This change is required for 2.6.36.

Change-Id: I5a712fb47e48c1bcc7ea2cfbf6c53c2b27627723
Reviewed-on: http://gerrit.openafs.org/2545
Reviewed-by: Derrick Brashear <shadow@dementia.org>
Tested-by: Derrick Brashear <shadow@dementia.org>