Merge from trunk:

Downgrade the log level of a worker MPM apr_proc_mutex_foo error
message when it occurs during restart (as we already do for a couple
of other calls).

Reviewed by: jorton, pquerna



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.0.x@202152 13f79535-47bb-0310-9956-ffa450edef68