Fix bogus log message when starting from a cleanly shut down state.

Fix bogus log message when starting from a cleanly shut down state.

In commit 70e81861fa to split xlog.c, I moved the startup code that
updates the state in the control file and prints out the "database
system was not properly shut down" message to the log, but I
accidentally removed the "if (InRecovery)" check around it. As a
result, that message was printed even if the system was cleanly shut
down, also during 'initdb'.

Discussion: https://www.postgresql.org/message-id/3357075.1645031062@sss.pgh.pa.us