etcupdate: Make diff -l actually work

[des]

Summary

While here, remove unnecessary blank lines.

MFC after: 1 week
Fixes: 6d65c91b9a47 ("etcupdate: fix arguments order of diff command")

[lytboris_gmail.com]

diff -l works for me as-is as intended:

>etcupdate diff -l

Changed: /etc/pam.d/ftpd

>etcupdate diff
Index: /etc/pam.d/ftpd
===================================================================
--- /etc/pam.d/ftpd (stock)
+++ /etc/pam.d/ftpd (local)
@@ -15,3 +15,4 @@

 # session
 session                required        pam_permit.so
+#XXX
\ No newline at end of file

Can you please provide an example where it fails to produce output needed?

[des]

# etcupdate diff -l | grep \^Changed
Changed: /etc/master.passwd
# etcupdate diff | grep \^Index     
Index: /etc/master.passwd
Index: /etc/pam.d/ftpd
Index: /etc/sysctl.conf
Index: /etc/group
Index: /etc/shells