Fix rm path for update package

[MB-Finski]

Fixes a bening bug where the nextcloud update package won't be removed after unpacking when the code is run inside a docker container.

Also, for readability/clarity, remove an unnecessary "/var/www" from a cp command.

Edit: As a side note, the ncp-update-nc script uses absolute and relative path references variably. Absolute references using either $BASEDIR or $DATADIR would perhaps make the script more robust and future proof. Would such a commit/pull request make sense?

Signed-off-by: MB-Finski [email protected]