devices: filesystem: Fix default virtiofs accessmode

We shouldn't use accessmode=mapped here, libvirt rejects it.
Let libvirt fill in a working default

Signed-off-by: Cole Robinson <crobinso@redhat.com>

tests/data/cli/compare/virt-install-many-devices.xml

@@ -522,6 +522,11 @@
       <source dir="/foo/source"/>
       <target dir="/bar/target"/>
     </filesystem>
+    <filesystem type="mount">
+      <source dir="/foo1"/>
+      <target dir="/bar1"/>
+      <driver type="virtiofs"/>
+    </filesystem>
     <interface type="user">
       <source portgroup="foo"/>
       <mac address="12:34:56:78:11:22"/>

tests/test_cli.py

@@ -695,6 +695,7 @@ source.reservations.managed=no,source.reservations.source.type=unix,source.reser
 --filesystem type=block,source.dev=/dev/foo,target.dir=/
 --filesystem type=ram,source.usage=1024,source.units=MiB,target=/
 --filesystem /foo/source,/bar/target,fmode=0123,dmode=0345
+--filesystem /foo1,/bar1,driver.type=virtiofs
 
 
 --soundhw default

virtinst/devices/filesystem.py

@@ -135,14 +135,22 @@ class DeviceFilesystem(Device):
     def set_defaults(self, guest):
         ignore = guest
 
-        if self.conn.is_qemu() or self.conn.is_lxc() or self.conn.is_test():
-            # type=mount is the libvirt default. But hardcode it
-            # here since we need it for the accessmode check
-            if self.type is None:
-                self.type = self.TYPE_MOUNT
+        if not (self.conn.is_qemu() or
+                self.conn.is_lxc() or
+                self.conn.is_test()):
+            return
 
-            # libvirt qemu defaults to accessmode=passthrough, but that
-            # really only works well for qemu running as root, which is
-            # not the common case. so use mode=mapped
-            if self.accessmode is None:
+        # type=mount is the libvirt default. But hardcode it since other
+        # bits like validation depend on it
+        if self.type is None:
+            self.type = self.TYPE_MOUNT
+
+        if self.accessmode is None:
+            if self.driver_type == "virtiofs":
+                # let libvirt fill in default accessmode=passthrough
+                pass
+            else:
+                # libvirt qemu defaults to accessmode=passthrough, but that
+                # really only works well for qemu running as root, which is
+                # not the common case. so use mode=mapped
                 self.accessmode = self.MODE_MAPPED