Make the new xprofile tests optional.

On Lucid at least, xprofile doesn't work. While others try to figure out the
underlying issue, this patch would just skip the tests if the profiling code
can not be imported.

Change-Id: I0fee3f729742cc727edc2adabb4ed782bea7798f
Change the default token logged length to 16

Based on comments from deployers at the Juno OpenStack summit,
limiting the default logged token length (to, by default, prevent
tokens from being fully logged) is a good idea.

Change-Id: I58980e85329d99de41f1c08f75e85973452317b1
Merge "Change the default token logged length to 16"