Migrate VM shares from 9p to virtiofs; update QEMU and doctor

cmd/qvm/doctor.go

@@ -10,6 +10,7 @@ import (
 	"qvm/internal/workspace"
 	"strconv"
 	"strings"
+	"syscall"
 
 	"github.com/spf13/cobra"
 )
@@ -232,7 +233,7 @@ func checkVirtiofsdSockets() []string {
 			continue
 		}
 
-		if err := process.Signal(os.Signal(nil)); err != nil {
+		if err := process.Signal(syscall.Signal(0)); err != nil {
 			issues = append(issues, fmt.Sprintf("Orphaned virtiofsd socket: %s (process %d not running)", sock, pid))
 		}
 	}