Replace a manual check of a VMIO candidate with vn_canvmio().  This silences an annoying warning in getblk() when VMIO'ing on a directory vnode, which can happen when vfs.vmiodirenable is 1.
Replace a manual check of a VMIO candidate with vn_canvmio().  This
silences an annoying warning in getblk() when VMIO'ing on a directory
vnode, which can happen when vfs.vmiodirenable is 1.

Bring the warning message in line with reality at the same time.

Submitted by:	hmp

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase