rpcaptache: fix typo upgradable vs upgradeable

dictionary says both is OK, but the apt bindings are not that flexible..

Signed-off-by: Manuel Traut <manut@linutronix.de>
apt/preferences remove newlines

apt.cache refuses to read a preferences file that contains only empty lines

Signed-off-by: Manuel Traut <manut@linutronix.de>