Only set the barrier flag if the feature was negotiated
Only set the barrier flag if the feature was negotiated

When the VirtIO barrier feature is not negotiated, the driver
must enforce the proper ordering for BIO_ORDERED BIOs. All the
in-flight BIOs must complete before starting the BIO, and the
ordered BIO must complete before subsequent BIOs can start.

Also fix a few whitespace nits.

Reported by:	neel
Approved by:	grehan (mentor)
MFC after:	3 days

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