test: re-enable and fix DeploymentAgentTest

[mattdibi]

In #5602 we disabled some tests that were failing due to the Java 17 change. This PR re-enables one of them.

We were getting the following error after switching to Java 17:

[ERROR] testRemovePackageToConfFile(org.eclipse.kura.deployment.agent.impl.DeploymentAgentTest)  Time elapsed: 1.299 s  <<< ERROR!
java.lang.NullPointerException: Cannot invoke "java.util.concurrent.ConcurrentHashMap.entrySet()" because "this.map" is null
	at org.eclipse.kura.deployment.agent.impl.DeploymentAgentTest.testRemovePackageToConfFile(DeploymentAgentTest.java:507)

[ERROR] testAddPackageToConfFileStoreException(org.eclipse.kura.deployment.agent.impl.DeploymentAgentTest)  Time elapsed: 0.025 s  <<< ERROR!
java.lang.NullPointerException: Cannot invoke "java.util.concurrent.ConcurrentHashMap.entrySet()" because "this.map" is null
	at org.eclipse.kura.deployment.agent.impl.DeploymentAgentTest.testAddPackageToConfFileStoreException(DeploymentAgentTest.java:421)

[ERROR] testRemovePackageToConfFileStoreException(org.eclipse.kura.deployment.agent.impl.DeploymentAgentTest)  Time elapsed: 0.025 s  <<< ERROR!
java.lang.NullPointerException: Cannot invoke "java.util.concurrent.ConcurrentHashMap.entrySet()" because "this.map" is null
	at org.eclipse.kura.deployment.agent.impl.DeploymentAgentTest.testRemovePackageToConfFileStoreException(DeploymentAgentTest.java:476)

This seems to be an issue with Mockito and spying Threads as per:

• Cannot spy on Thread in Java 17 mockito/mockito#2628
• Switch the default mockmaker to the inline mockmaker on JDK 17+ mockito/mockito#2589

As suggested in mockito/mockito#2628, switching to mockito-inline seems to fix it.

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Note: there seems to be another issue with this same test suite related to mockserver. When running these tests we get:

java.lang.IllegalStateException: javax.security.cert.CertificateException: Could not find class: java.lang.ClassNotFoundException: com/sun/security/cert/internal/x509/X509V1CertImpl

which is related to mock-server/mockserver#1739.

This does not break our current tests because, even if it fails to decode the client certificate, it proceeds with the rest of the test anyway.