build: disable stack-trace trimming in surefire

Motivation:

Surefire has a feature where it tries to guess initial frames of a
stack-trace that comes from "boring" code (such as JRE libraries).
Unfortunately it is both enabled by default (to solicit feedback) and
quite broken, as it often considers dCache code as "not of interest".

Modification:

Disable stack-trace filtering in surefire.

Result:

Unit-test stack-traces (ones printed when running unit tests) now
include all elements (method calls) up to the point where the exception
was thrown.  This results in longer stack-traces, but eliminates the
risk that surefire mistakenly excludes frames that are important in
understanding what just happened.

Target: master
Requires-notes: no
Requires-book: no
Patch: https://rb.dcache.org/r/13025/
Acked-by: Lea Morschel

pom.xml

@@ -1126,6 +1126,11 @@
                     <groupId>org.apache.maven.plugins</groupId>
                     <artifactId>maven-surefire-plugin</artifactId>
                     <version>3.0.0-M4</version>
+                    <configuration>
+                        <!-- Disable stack-trace trimming as
+                             surefire makes bad decisions too often. -->
+                        <trimStackTrace>false</trimStackTrace>
+                    </configuration>
                 </plugin>
                 <plugin>
                     <groupId>org.apache.maven.plugins</groupId>