Add two spaces between md5sum and filename to be compatible with GNU coreutils md5sum.

As mentioned here, you get a "no properly formatted MD5 checksum lines found" error with the current output: http://en.wikipedia.org/wiki/Md5sum

As an aside, all the other md5sums files for debs on my systems omit everything, including the leading / of the filename, like so (I'm guessing this is to ensure you're referencing the real file in root):
head -n 1 /var/lib/dpkg/info/apache2.2-common.md5sums
9dfb379b4d9ba592397cd8b3d35287a0  usr/sbin/a2enmod