User `isolate` should be added as a system user

[zimtsui]

isolate/debian/isolate.postinst

Line 22 in cf03a90

adduser --quiet --disabled-login --ingroup isolate --home /nonexistent --no-create-home --shell /bin/false $ADDUSER_CMT "" isolate

Option --system of adduser is missing, resulting that the user isolate appears in login screen.

[prandla]

There is a comment 5 lines above the snippet you quoted which explains why --system is not used here.

isolate/debian/isolate.postinst

Lines 12 to 15 in cf03a90

	# By Debian policy, it should be a system user. However,
	# we need to have a subuid range assigned which adduser
	# cannot do for system users. I promise to switch to
	# system users when somebody teaches adduser better manners. --mj

[prandla]

for reference, here is the debian bug report about adduser's behavior: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1132734