provision: Send 'update schema now' action after each schema modify operation

This commands reloads the schema information into the server cache.
provision: Send 'update schema now' in provision_schema function

Instead of calling modify_schema function explicitly, do it inside the
provision_schema function. This way it reduces the verbosity on command output
and is integrated inside the ldb transaction.
Merge pull request #58 from Zentyal/scabrero/provision-update-schema-now

provision: Send 'update schema now' action after each schema modify oper...