update ec2 plugin tests

[car-roll]

AmazonEC2Cloud constructor variable name was changed in jenkinsci/ec2-plugin#892

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[car-roll]

Receiving the following failure for MesosCloud in a specific test, EC2CloudTest.configure_ec2_cloud 🤔

  14.125 [id=34]	WARNING	jenkins.model.Jenkins$5#runTask: MesosCloud.init failed perhaps due to plugin dependency issues
java.lang.NoSuchFieldError: AUTOMATIC_SLAVE_LAUNCH
	at org.jenkinsci.plugins.mesos.MesosCloud.init(MesosCloud.java:118)
Caused: java.lang.reflect.InvocationTargetException
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	at hudson.init.TaskMethodFinder.invoke(TaskMethodFinder.java:109)

[car-roll]

will move back to ready when jenkinsci/ec2-plugin#892 has been merged and released

[car-roll]

jenkinsci/ec2-plugin#892 has now been merged, PR is ready for review