box: log error that caused initial checkpoint failure

Currently, we just panic without providing any additional information
if we failed to create the initial checkpoint on bootstrap. This
complicates trouble shooting. Let's replace `panic()` with `say_error()`
and raise the exception that caused the failure. The exception will be
caught by `box_cfg()`, which will log it and then panic.

NO_DOC=error logging
NO_TEST=error logging
NO_CHANGELOG=error logging

(cherry picked from commit e1b5114d99ed2f224e9e9a17bf29882e50be3653)