Log exceptions when creating share

Because the exceptions don't always contain a useful message for the UI,
but also because in some cases we need to find out what went wrong.

In some setups, a ShareNotFoundException might happen during creation
when we try to re-read the just written share. Usually related to Galera
Cluster where node syncing wait is not enabled.

Signed-off-by: Vincent Petry <vincent@nextcloud.com>