Only run 4 instances max in churn.

Change-Id: I0e559e7b8b04a0b5227de2eeea3ff451eef4dc3c
Merge branch 'testing' of git.qa1.eucalyptus-systems.com:qa-repos/eutester into testing
Set EUCALYPTUS env var, not euca sbin path when calling installer
Merge branch 'testing' of git.qa1.eucalyptus-systems.com:qa-repos/eutester into testing