mod_reqtimeout: fix default_[stage]_rate_factor initializations.

r1853901 lowercased the [stage] for MRT_DEFAULT_[stage]_* macros but missed
to change the ones used in reqtimeout_hooks() to initialize the default rate
factors, leading to no default rate in 2.4.39. Fix that now. PR 63325.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1857129 13f79535-47bb-0310-9956-ffa450edef68