This change adds two log packages. One for the external go-ceph
consumers under common/log, and one for the internal use within the
go-ceph code under internal/log. The external package exports two
functions for consumers, SetWarnf() and SetDebugf(), that set a
logger for warnings and debug messages respectively. They take a
log.Printf compatible function as argument.
The internal package exports these functions as Warnf() and Debugf(),
which can be used by the go-ceph code to log warnings and debug
messages.
Signed-off-by: Sven Anderson <sven@redhat.com>