blackbox: use a human readable version of the default
Now that the default value is also converted we can use a human readable version
for it. This will be useful if we start to automatically display the default
config value in various place.
pager.pager=p0 # $TESTTMP/sysrc:4
ui.editor=e1 # $TESTTMP/userrc:2
pager.pager=p2 # $PAGER
ui.editor=e1 # $TESTTMP/userrc:2