[maven-release-plugin] prepare release ec2-1.21
[maven-release-plugin] prepare for next development iteration
updates retention stategy to support negative values

Negative values in the retention strategy means that the instance will
continue to remain idle during the already charged billing period.

For instance, if a slave comes online, runs a 5 minute build, and then
terminates after 20 minutes, the instance was shutdown with 35 minutes
still available in the billing period.  If another build were to be
requested 10 minutes later, another hour would be charged.  This strategy
helps keep slaves alive for as long as possible, but terminates them
before they incur additional cost.
Merge pull request #80 from valdisrigdon/neg_retention

updates retention stategy to support negative values
fixes form validation for negative idle times
Merge pull request #81 from valdisrigdon/neg_retention

fixes form validation for negative idle times
Implementing JENKINS-22141 Add Support for Dedicated Tenancy Option:
 - Added checkbox for dedicated tenancy to Slave Template.
 - Added help entry for dedicated tenancy option to clarify its usage.
 - Added support for dedicated tenancy for OnDemand Instances only, as this doesn't pertain to Spot Instances.
 - Updated SlaveTemplateTest.testConfigRoundtrip to ensure useDedicatedTenancy is set as expected.
Merge pull request #83 from rsennewald/JENKINS-22141

Implementing JENKINS-22141 Add Support for Dedicated Tenancy Option.