oslo config code treat treats the '$' as a special character and it
needs to be delimited when using within a string. There are two ways of
doing this, '$$' or '\$'. We document the former but not the latter. Fix
this.
Change-Id: I37cdf31ba1c2924779a46b1a2eeabb66c46a2212
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>
Closes-Bug: #1872839