Small refactoring in Openstack error handling
Small refactoring in Openstack error handling

Signed-off-by: Tobias Zipfel <087edddb12ac44c92ffe5bde7e37fdd0c506a257@de.ibm.com>

cloudfoundry-incubator/bits-service,petergtz/bitsgo,cloudfoundry-incubator/bits-service,cloudfoundry-incubator/bits-service,petergtz/bitsgo,cloudfoundry-incubator/bits-service,cloudfoundry-incubator/bits-service