Log exception details.

When there is an error while initializing the backing store,
log entrires are now displaying more details specifying
the reason of failure.

Also instead of normal info message, log entries display
warnings in this case.

Fixes: bug #1103073
Change-Id: Icb7cc3c27325cfb0e4d62f466d28ecf9995d91ac
Merge "Log exception details."