ZTS: Fix redacted_send failures on FreeBSD

We're seeing failures for redacted_deleted and redacted_mount
on FreeBSD 13-15:

    09:58:34.74 diff: /dev/fd/3: No such file or directory
    09:58:34.74 ERROR: diff /dev/fd/3 /dev/fd/4 exited 2

The test was trying to diff the file listings between two directories to
see if they are the same.  The workaround is to do a string comparison
of the directory listings instead of using `diff`.

Signed-off-by: Tony Hutter <hutter2@llnl.gov>

tests/zfs-tests/tests/functional/redacted_send/redacted_deleted.ksh

@@ -96,7 +96,7 @@ log_must zfs destroy -R $clone2
 log_must eval "zfs send -i $sendfs#book2 --redact book3 $sendfs@snap2 >$stream"
 log_must eval "zfs recv $recvfs <$stream"
 log_must mount_redacted -f $recvfs
-log_must diff <(ls $send_mnt) <(ls $recv_mnt)
+log_must [ "$(ls $send_mnt)" == "$(ls $recv_mnt)" ]
 log_must zfs destroy -R $recvfs
 log_must zfs rollback -R $sendfs@snap
 

tests/zfs-tests/tests/functional/redacted_send/redacted_mounts.ksh

@@ -71,8 +71,7 @@ log_must ismounted $recvfs
 # deleted.
 contents=$(log_must find $recv_mnt)
 contents_orig=$(log_must find $send_mnt)
-log_must diff <(echo ${contents//$recv_mnt/}) \
-    <(echo ${contents_orig//$send_mnt/})
+log_must [ "${contents//$recv_mnt/}" == "${contents_orig//$send_mnt/}" ]
 log_must zfs redact $sendvol@snap book2 $clonevol@snap
 log_must eval "zfs send --redact book2 $sendvol@snap >$stream"
 log_must eval "zfs receive $recvvol <$stream"
@@ -103,7 +102,6 @@ log_must mount_redacted -f $recvfs
 log_must ismounted $recvfs
 contents=$(log_must find $recv_mnt)
 contents_orig=$(log_must find $send_mnt)
-log_must diff <(echo ${contents//$recv_mnt/}) \
-    <(echo ${contents_orig//$send_mnt/})
+log_must [ "${contents//$recv_mnt/}" == "${contents_orig//$send_mnt/}" ]
 
 log_pass "Received redacted streams can be mounted."