Skipper manifests not getting deleted after stream deployment

[dturanski]

Temporary files containing skipper package metadata should be cleaned up after deployment
e.g.

8.0K	tmp/streampackages9162299677790935257
4.0K	tmp/streampackages1007424933889654655
4.0K	tmp/streampackages3613564728514687451
8.0K	tmp/streampackages5352378485999921593
8.0K	tmp/streampackages1319042573028839470
8.0K	tmp/streampackages7248908537943486036
4.0K	tmp/streampackages5429856046145102856
8.0K	tmp/streampackages2686614591391408289
8.0K	tmp/streampackages2451070546720853505
8.0K	tmp/streampackages4768415752267910759
8.0K	tmp/streampackages1430378488614443187
4.0K	tmp/streampackages7909454466146896008
4.0K	tmp/streampackages2207751261229937393
4.0K	tmp/streampackages5232007855539163736

Observed with Cloud Foundry Deployer

[dturanski]

see https://github.com/spring-cloud/spring-cloud-dataflow/blob/b6d094924d86fff3530cf83aefe6530f8ce10a55/spring-cloud-dataflow-server-core/src/main/java/org/springframework/cloud/dataflow/server/stream/SkipperStreamDeployer.java#L376