Refactor: scheduler: drop pe_err() and pe_warn()

The scheduler has three sets of special log functions:

• pcmkconfig_err() and pcmkconfig_warn() set the crm_config_error and crm_config_warning variables;
• pcmksched_err() and pcmksched_warn() set the was_processing_error and was_processing_warning variables; and
• pe_err() and pe_warn() set both sets of variables

Now that configuration problems are treated as also being processing problems,
there is no need for the last set of functions, which can be replaced with
the config problem functions (or the processing problem functions where they
weren't being used correctly to begin with).