benchmark-reverse: add file reads

Note: find currently complains like this:

 find: failed to read file names from file system at or below
 ‘/tmp/linux-3.0.reverse.mnt.vNI’: No such file or directory

I have analyzed this and it is caused by the non-stable inode numbers
that gocryptfs -reverse uses. Will be fixed in a later commit.

benchmark-reverse.bash

@@ -46,4 +46,5 @@ function etime {
 
 echo -n "LS:  "
 etime ls -lR $MNT
-
+echo -n "CAT: "
+etime find $MNT -type f -exec cat {} +