Fix time printing in key files

Fix time printing in key files

Don't strip off the final character when printing times in key files.

With the introduction of 'rndc dnssec -status' we introduced
'isc_stdtime_tostring()'. This changed in behavior such that it was no
longer needed to strip of the final '\n' of the string format
datetime. However, in 'printtime()' it still stripped the final
character.