virt-aa-helper: allow sysfs path used for vhost-scsi

When a vhost scsi device is hotplugged virt-aa-helper is called to
add the respective path.
For example the config:
  <hostdev mode='subsystem' type='scsi_host' managed='no'>
    <source protocol='vhost' wwpn='naa.50014059de6fba4f'/>
  </hostdev>
Will call it to add:
 /sys/kernel/config/target/vhost//naa.50014059de6fba4f

But in general /sys paths are filtered in virt-aa-helper.c:valid_path
To allow the path used for vhost-scsi we need to add it to the list of
known and accepted overrides.

Fixes: https://bugs.launchpad.net/ubuntu/+source/libvirt/+bug/1829223Signed-off-by: NChristian Ehrhardt <christian.ehrhardt@canonical.com>
Reviewed-by: NDaniel P. Berrangé <berrange@redhat.com>

src/security/virt-aa-helper.c

@@ -510,8 +510,9 @@ valid_path(const char *path, const bool readonly)
     };
     /* override the above with these */
     const char * const override[] = {
-        "/sys/devices/pci",              /* for hostdev pci devices */
-        "/etc/libvirt-sandbox/services/" /* for virt-sandbox service config */
+        "/sys/devices/pci",                /* for hostdev pci devices */
+        "/sys/kernel/config/target/vhost", /* for hostdev vhost_scsi devices */
+        "/etc/libvirt-sandbox/services/"   /* for virt-sandbox service config */
     };
 
     const int nropaths = ARRAY_CARDINALITY(restricted);