Convert SSHFP records into structured data

Previously the SSHFP records were printed as a string, and in the
presence of multiple keys, the records would be combined, separated by
newline.  Since anyone taking advantage of the SSHFP records is likely
needing to to add each record independently to their DNS, they will
likely have to split the string and munge the data.

Since Facter 2 supports structured data, this work converts the SSHFP
fact records into an array, so that one may simply call 'each'.

Here also we clean up some whitespace.