Removed 2 unnecessary stubbings in NetconfSessionTest.java

[ARUS2023]

In our analysis of the project, we observed that there are 8 tests NetconfSessionTest.java.GIVEN_getCandidateConfig_WHEN_syntaxError_THEN_throwNetconfException, NetconfSessionTest.java.GIVEN_getRunningConfig_WHEN_syntaxError_THEN_throwNetconfException, NetconfSessionTest.java.GIVEN_createSession_WHEN_devicePromptWithoutLF_THEN_correctResponse,
NetconfSessionTest.java.GIVEN_executeRPC_WHEN_syntaxError_THEN_throwNetconfException,
NetconfSessionTest.java.GIVEN_stringWithoutRPC_fixupRPC_THEN_returnStringWrappedWithRPCTags,
NetconfSessionTest.java.GIVEN_stringWithRPCTags_fixupRPC_THEN_returnWrappedString,
NetconfSessionTest.java.GIVEN_stringWithTag_fixupRPC_THEN_returnWrappedString,
and NetconfSessionTest.java.GIVEN_nullString_WHEN_fixupRPC_THEN_throwException in NetconfSessionTest.java
that did not execute two stubbings in the setUp method causing them to be unnecessary.
There are also 7 tests: NetconfSessionTest.java.loadXmlConfigurationWillFailIfResponseIsOkWithErrors,
NetconfSessionTest.java.loadXmlConfigurationWillFailIfResponseIsNotOk,
NetconfSessionTest.java.loadXmlConfigurationWillSucceedIfResponseIsOk,
NetconfSessionTest.java.loadTextConfigurationWillFailIfResponseIsOkWithErrors,
NetconfSessionTest.java.loadTextConfigurationWillFailIfResponseIsNotOk,
NetconfSessionTest.java.loadTextConfigurationWillSucceedIfResponseIsOk,
and NetconfSessionTest.java.WHEN_instantiated_THEN_fetchHelloFromServer,
that did not execute the stubbing when(mockChannel.getInputStream()).thenReturn(inPipe) in the setUp method causing it to be unnecessary.

Unnecessary stubbings are stubbed method calls that were never realized during test execution. Mockito recommends to remove unnecessary stubbings (https://www.javadoc.io/doc/org.mockito/mockito-core/latest/org/mockito/exceptions/misusing/UnnecessaryStubbingException.html).

We propose below a solution to remove the unnecessary stubbings.

[peterjhill]

#77
covers all these I think