Analysis:
========
As part of performance schema enhancements following tables
were added to provide enhanced replication monitoring
information.

Table: replication_applier_status_by_coordinator
  --The status of coordinator thread was reported as part of
    this table in multi threaded slave mode.
  --The status of SQL thread was reported as part of this
    table in single threaded slave mode.
Table: replication_applier_status_by_worker
  --The status of worker threads is reported in this table.

In case of single threaded slave mode report the status of
SQL thread as part of 'replication_applier_status_by_worker'
table.

Fix:
===
Added code to display SQL thread's status information as
part of 'replication_applier_status_by_worker' table in
single threaded slave(STS) mode. Hence
'replication_applier_status_by_coordinator' table will
be empty now in STS mode. MTS mode will be reported as it
was earlier.