Add testvnd.sh test script

As part of this, change the "run" script to allow certain scripts to
be run as root only.

Change-Id: I846e41037f9d4f6c7fc0b5ea8250303a7bd72f5d

test/blocktest/test.sh

@@ -62,3 +62,7 @@
 # AHCI ATAPI TEST (for SATA CD-ROM devices)
 
 #block_test /dev/c2d1 "ro,sector=2048,min_read=2,element=2,max=4194304"
+
+# VND TEST (for configured vnode disk devices)
+
+#block_test /dev/vnd0 "rw,min_read=1,min_write=1,element=1,max=16777216"