test_distribution should depend on what it tests
test_distribution should depend on what it tests

Omitting this resulted in a spooky error when testing only this target
in isolation:

```
===================== ERRORS =====================
 ERROR collecting tests/python/pants_test/java/distribution/test_distribution.py
tests/python/pants_test/java/distribution/test_distribution.py:19: in <module>
    from pants.java.distribution.distribution import Distribution, DistributionLocator
src/python/pants/java/distribution/distribution.py:19: in <module>
    from pants.java.util import execute_java
src/python/pants/java/util.py:15: in <module>
    from pants.java.nailgun_executor import NailgunExecutor
src/python/pants/java/nailgun_executor.py:23: in <module>
    from pants.pantsd.process_manager import ProcessGroup, ProcessManager
src/python/pants/pantsd/process_manager.py:16: in <module>
    import psutil
E   ImportError: No module named psutil
============ 1 error in 0.07 seconds =============
```

Bugs closed: 2712

Reviewed at https://rbcommons.com/s/twitter/r/3243/

wisechengyi/pants,benjyw/pants,gmalmquist/pants,gmalmquist/pants,pantsbuild/pants,ericzundel/pants,ericzundel/pants,ericzundel/pants,pombredanne/pants,baroquebobcat/pants,dturner-tw/pants,benjyw/pants,tdyas/pants,baroquebobcat/pants,lahosken/pants,gmalmquist/pants,15Dkatz/pants,15Dkatz/pants,tdyas/pants,fkorotkov/pants,dturner-tw/pants,pombredanne/pants,gmalmquist/pants,mateor/pants,mateor/pants,dbentley/pants,peiyuwang/pants,gmalmquist/pants,manasapte/pants,lahosken/pants,fkorotkov/pants,UnrememberMe/pants,jsirois/pants,pantsbuild/pants,twitter/pants,15Dkatz/pants,lahosken/pants,cevaris/pants,15Dkatz/pants,UnrememberMe/pants,kwlzn/pants,fkorotkov/pants,twitter/pants,cevaris/pants,foursquare/pants,dturner-tw/pants,fkorotkov/pants,ericzundel/pants,ity/pants,dturner-tw/pants,twitter/pants,dbentley/pants,baroquebobcat/pants,peiyuwang/pants,dturner-tw/pants,cevaris/pants,foursquare/pants,manasapte/pants,foursquare/pants,dturner-tw/pants,ity/pants,benjyw/pants,kwlzn/pants,fkorotkov/pants,pombredanne/pants,cevaris/pants,tdyas/pants,UnrememberMe/pants,wisechengyi/pants,twitter/pants,manasapte/pants,ericzundel/pants,fkorotkov/pants,lahosken/pants,landism/pants,benjyw/pants,pantsbuild/pants,wisechengyi/pants,peiyuwang/pants,tdyas/pants,15Dkatz/pants,landism/pants,dbentley/pants,mateor/pants,pombredanne/pants,cevaris/pants,lahosken/pants,lahosken/pants,dturner-tw/pants,UnrememberMe/pants,tdyas/pants,baroquebobcat/pants,UnrememberMe/pants,mateor/pants,lahosken/pants,15Dkatz/pants,UnrememberMe/pants,pombredanne/pants,ericzundel/pants,pantsbuild/pants,foursquare/pants,gmalmquist/pants,15Dkatz/pants,manasapte/pants,foursquare/pants,15Dkatz/pants,ity/pants,cevaris/pants,tdyas/pants,benjyw/pants,ity/pants,twitter/pants,jsirois/pants,baroquebobcat/pants,kwlzn/pants,foursquare/pants,ity/pants,ericzundel/pants,landism/pants,kwlzn/pants,tdyas/pants,lahosken/pants,ericzundel/pants,wisechengyi/pants,UnrememberMe/pants,peiyuwang/pants,pantsbuild/pants,dbentley/pants,UnrememberMe/pants,landism/pants,wisechengyi/pants,twitter/pants,peiyuwang/pants,pombredanne/pants,pantsbuild/pants,peiyuwang/pants,ity/pants,manasapte/pants,dbentley/pants,foursquare/pants,pantsbuild/pants,manasapte/pants,ity/pants,foursquare/pants,benjyw/pants,tdyas/pants,wisechengyi/pants,mateor/pants,twitter/pants,kwlzn/pants,mateor/pants,wisechengyi/pants,landism/pants,landism/pants,baroquebobcat/pants,manasapte/pants,tdyas/pants,baroquebobcat/pants,jsirois/pants,dbentley/pants,mateor/pants,fkorotkov/pants,dbentley/pants,peiyuwang/pants,baroquebobcat/pants,wisechengyi/pants,pombredanne/pants,fkorotkov/pants,baroquebobcat/pants,twitter/pants,wisechengyi/pants,kwlzn/pants,cevaris/pants,kwlzn/pants,benjyw/pants,peiyuwang/pants,UnrememberMe/pants,gmalmquist/pants,mateor/pants,landism/pants,foursquare/pants,twitter/pants,landism/pants