Linux 4.2 compat: vfs_rename()

Linux 4.2 compat: vfs_rename()

Attempting to perform a vfs_rename() on Linux 4.2 and newer kernels
results in an EACCES error.  Rather than attempting to add and
maintain more ugly compatibility code it's best to just retire
this interface.  As a first step the SPLAT test is disabled for
Linux 4.2 and newer kernels.

  vn_rename: Failed vn_rename /tmp/vn.tmp.1 -> /tmp/vn.tmp.2 (13)

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue zfsonlinux/zfs#3653