Fix locking bugs that could corrupt pg_control.

 Fix locking bugs that could corrupt pg_control.
 
 The redo routines for XLOG_CHECKPOINT_{ONLINE,SHUTDOWN} must acquire
 ControlFileLock before modifying ControlFile->checkPointCopy, or the
 checkpointer could write out a control file with a bad checksum.
 
 Likewise, XLogReportParameters() must acquire ControlFileLock before
 modifying ControlFile and calling UpdateControlFile().
 
 Back-patch to all supported releases.
 
 Author: Nathan Bossart <bossartn@amazon.com>
 Author: Fujii Masao <masao.fujii@oss.nttdata.com>
 Reviewed-by: Fujii Masao <masao.fujii@oss.nttdata.com>
 Reviewed-by: Michael Paquier <michael@paquier.xyz>
 Reviewed-by: Thomas Munro <thomas.munro@gmail.com>
 Discussion: https://postgr.es/m/70BF24D6-DC51-443F-B55A-95735803842A%40amazon.com