build-sys: don't install quotaon.service twice

quotaon.service is already installed through dist_systemunit_DATA, so it doesn't
need to be added to nodist_systemunit_DATA.  Installing the same file twice
results in a race condition where the install process can fail.

https://bugs.freedesktop.org/show_bug.cgi?id=65659

[zj: actually remove quotaon.service from the other list.]

Makefile.am

@@ -389,7 +389,6 @@ dist_systemunit_DATA = \
 	units/sound.target \
 	units/bluetooth.target \
 	units/smartcard.target \
-	units/quotaon.service \
 	units/systemd-ask-password-wall.path \
 	units/systemd-ask-password-console.path \
 	units/systemd-udevd-control.socket \