Fix UART console on FreeBSD 12.1 and CURRENT.

bhyve was doing UART console emulation on fd 0 for both reads and
writes.  Commits r346550 and r352720 changed it to use fd 0 for input
and fd 1 for output on console.

Fix vm-bhyve to not redirect fd 1.

Fixes #332.

lib/vm-run

@@ -272,7 +272,7 @@ vm::run(){
               ${_devices} \
               ${_iso_dev} \
               ${_comstring} \
-              ${_name} >>"${_logpath}" 2>&1
+              ${_name} 2> "${_logpath}"
 
         # get bhyve exit code
         _exit=$?