The threee tags `<name>`, `</name>` and `<command>` were frequently used
with a leading space that this removes. The reason this habbit is so
widespread in testcases is probably that they have been copy and pasted.
Hence, fixing them all now might curb this practice from now on.
Closes#12028
RFC 4616 specifies the authzid is optional in the client authentication
message and that the server will derive the authorisation identity
(authzid) from the authentication identity (authcid) when not specified
by the client.
As the email protocols implement SASL authentication rather than IMAP,
POP3 and SMTP specific authentication, updated the authentication
keywords to reflect this.