systemd-systemctl-native: don't care about line endings

It's possible for a service file to accidentally contain mixed line endings, but
the string cleanup code was assuming Unix endings.

[ YOCTO #13535 ]

(From OE-Core rev: 7aaa9200b5ba2cba92ee1ed7003d54848498b37d)

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>