scriptlet/01-alternatives.sh: add --quiet to --install operations

Whilst upgrading systemd, these warnings always gets printed:

update-alternatives: warning: forcing reinstallation of alternative /usr/bin/systemctl because link group runlevel is broken
update-alternatives: warning: forcing reinstallation of alternative /usr/bin/systemctl because link group reboot is broken
update-alternatives: warning: forcing reinstallation of alternative /usr/bin/systemctl because link group shutdown is broken
update-alternatives: warning: forcing reinstallation of alternative /usr/bin/systemctl because link group poweroff is broken
update-alternatives: warning: forcing reinstallation of alternative /usr/bin/systemctl because link group halt is broken
update-alternatives: warning: forcing reinstallation of alternative /usr/bin/systemctl because link group telinit is broken
update-alternatives: warning: forcing reinstallation of alternative /usr/lib/systemd/systemd because link group init is broken

However, the referenced files were always present, even after replacement.
Adding the --quiet flag to suppress these seemingly nonsensical warnings and,
since --quiet will still output errors when they occur (when the user should
actually be alerted), this flag should be fine being added on as default.

Ref: openSUSE does this repository-wide but for a different reason, but it
     should prove that this hack is safe enough.

     https://bugzilla.opensuse.org/show_bug.cgi?id=1172896#c3

Author: MingcongBai

scriptlet/01-alternatives.sh

@@ -4,7 +4,7 @@
 # a more precise one
 # addalt link name path prio
 addalt(){
-	echo "update-alternatives --install $(argprint "$@")" >> abscripts/postinst
+	echo "update-alternatives --install $(argprint "$@") --quiet" >> abscripts/postinst
 	echo 'if [ "$1" != "upgrade" ]; then' >> abscripts/prerm
 	echo "	update-alternatives --remove $(argprint "$2" "$3")" >> abscripts/prerm
 	echo "fi" >> abscripts/prerm