To make our code consistent will be better to use one decorator for all
operations which require retry on exceptions. RetryDecorator from
oslo_service is operated with green threads and probably is not a best
choice for the decorator of retry operations in murano. An obsolete
custom retry decorator was removed too.
Closes-Bug: 1559890
Change-Id: I7b1d0675e5628769d7e618d7b6118478039ac2db
d0c23103ee