Update example kadmin getprinc enctype display

In kadmin_local.rst, update the example to reflect the new way we
display enctypes.

ticket: 7890 (new)
target_version: 1.12.2
tags: pullup
Improve salt type display in kadmin getprinc

In krb5_salttype_to_string, output the salt type name we would
recognize as input.

In the output of getprinc, display the enctype and salt type in a form
we would accept--either enctype:salttype if the salt type is not the
default, or just the enctype if it is.

Update t_mkey.py and t_salt.py to expect the new output format.
Update documentation examples to show the new format.

ticket: 5958