Use LogMessage.format when possible

[philwebb]

Spring Framework has introduced a nice LogMessage class that we might be able to use in a few placed to reduce the need for isWarnEnabled etc.

[pkostrzewa]

Can I work on this one?

[philwebb]

@pkostrzewa Thanks for the offer, but the changes are likely to require some careful review (it's not necessary to change all log messages). I really just added the issue as a placeholder for something we'll look at after 2.2.