php7: fix config file upgrade issue (fixes #14623)

php7: fix config file upgrade issue (fixes #14623)

The addressed issue is related to #6893 as its resolution
is actually causing the problem.

When changing the priority of the config file it happens
that after a sysupgrade the previous file is restored
and the new file is added, ending up in a situation
like this:

/etc/php7/15_openssl.ini
/etc/php7/20_openssl.ini

Causing a double extension=openssl.so to be parsed,
which is not appropriate and leads to error message.

The same problem might also occur for mysqli since there
was also a priority change - let's take care about this
at the same time.

The solution is to remove one of the files. Since it is
a configuration file, the user might have adjusted it, so
lets just use the previous version to replace the new
installed version.

Signed-off-by: Michael Heimpold <mhei@heimpold.de>