Bug#927395: Do not touch(1) update-exim4.conf.conf for no good reason

[積丹尼 Dan Jacobson]

https://www.debian.org/doc/debian-policy/ap-pkg-conffiles.html :
"Note that a package should not **modify** a dpkg-handled conffile in its
maintainer scripts. Doing this will lead to dpkg giving the user
confusing and possibly dangerous options for conffile update when the
package is upgraded."

>> $ stat /etc/exim4/update-exim4.conf.conf
>> Modify: 2019-04-18 01:32:53.473019451 +0800 <------------THIS

Modified!

Anyway to compare two things one could use
$ test "$THING!" = "$THING2"
No need to worry about accidentally leaving temp files on disk,
which is a must less risk than failed unnecessary writes to a file that
you won't end up changing anyway. You might argue that well, the md5sum
doesn't change. But then I will argue back that what if I updated the
modification dates of all the files in your home directory? That would
make the whole concept of the date stamp of a file meaningless.