slaprunner SR: define SLA from resilience test.
slaprunner SR: use good scalability branch for erp5.util when development.
Slaprunner SR: resilience test: decrease periodicity of backup to speed up test.
resiliency: takeover: fix missing import.
slaprunner SR: don't hardcode resiliency parameters for exporter instance.
slaprunner: don't check certificate for importer.
Resiliency: Only keep 10 increments of backup.

Also allow to bypass default value.