[releng] Fix surefire config

It made reference to an undefined variable `${workspace.root.folder}`.
Correct would have been `${workspace.root.dir}`, defined in the maven
configuration at .mvn/maven.config.

However, even if corrected running JUnit tests in Eclipse doesn't work
(undefined reference to `session.rootDirectory`) since there is no maven
session.

So fix this differently. As for all our Java projects the maven
workspace root is at `${project.basedir}/..` let's use that. That works
in Eclipse and on the command-line.

Author: tomaswolf

pom.xml

@@ -1280,7 +1280,7 @@
                         <java.awt.headless>true</java.awt.headless>
                         <org.slf4j.simpleLogger.logFile>System.out</org.slf4j.simpleLogger.logFile>
                         <org.apache.sshd.test.timeout.factor>${sshd.tests.timeout.factor}</org.apache.sshd.test.timeout.factor>
-                        <logback.configurationFile>${workspace.root.folder}${file.separator}sshd-common${file.separator}src${file.separator}test${file.separator}resources${file.separator}logback-test.xml</logback.configurationFile>
+                        <logback.configurationFile>${project.basedir}${file.separator}..${file.separator}sshd-common${file.separator}src${file.separator}test${file.separator}resources${file.separator}logback-test.xml</logback.configurationFile>
                     </systemPropertyVariables>
                     <trimStackTrace>false</trimStackTrace>
                     <!-- lets re-run the failed test one more time, just to be sure -->