[krbdev.mit.edu #7792] supported_enctypes parsing does not handle DEFAULT

[Benjamin Kaduk via RT]

The parsing used by kadm5_get_config_params (i.e., krb5_string_to_keysalts) does not handle 
DEFAULT (as krb5int_parse_enctype list, used to parse the other enctype profile variables, does), 
though our documentation claims that supported_enctypes will honor DEFAULT.

Additionally, kadm5_get_config_params ignores the return value of krb5_string_to_keysalts, so 
errors in the supported_enctype list only result in kadmind failing to startup if the first entry is 
invalid.

Reported by CSights <cwseys at physics.wisc.edu> in Debian bug 730583.