systemd: use if..then in prerm scriptlet

systemd: use if..then in prerm scriptlet

Using the [ test ] && foo construct in the prerm scriptlet causes
the prerm scriptlet to fail if the final test condition fails, which
with rpm prevents the removal of the package. Switch to using
if;then;fi instead, since it doesn't cause the scriptlet to fail.

Signed-off-by: Daniel McGregor <daniel.mcgregor@vecima.com>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briand@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>