Emit log when restore_command succeeds but archived file faills to be restored.

Emit log when restore_command succeeds but archived file faills to be restored.

Previously, when restore_command claimed to succeed but failed to restore
the file with the right name, for example, due to mis-configuration of
restore_command, no log message was reported. Then the recovery failed
later with an error message not directly related to the issue.

This commit changes the recovery so that a log message is emitted in
this error case. This would enable us to investigate what happened in
this case more easily.

Author: Jeff Janes, Fujii Masao
Reviewed-by: Pavel Borisov, Kyotaro Horiguchi
Discussion: https://postgr.es/m/CAMkU=1xkFs3Omp4JR4wMYWdam_KLuj6LXnTYfU8u3T0h=PLLMQ@mail.gmail.com