[JUNIT] Fix SharedResourcesManagerTest's invocation order dependency

The SharedResourcesManagerTest made use of Stream but forgot to reset it
after reading. As an unwanted result, the two test cases led to
different results depending on their order of invocation (by luck, they
succeeded using the order they were positioned in the class).

JUnit does not guarantee the ordering of test-method invocation
(http://junit.sourceforge.net/doc/faq/faq.htm#tests_2).

Change-Id: I95694796ac711925d7b86e5007937ca4062c8188
Reviewed-on: http://saros-build.imp.fu-berlin.de/gerrit/878
Reviewed-by: Stefan Rossbach <srossbach@arcor.de>
Tested-by: Jenkins CI