MDL-48194 testing: Adjust naming of testsuites in phpunit.xml

This will make it easier to run phpunit for a specific component by making
all testsuite names consistent, guessable, and in-line with the naming of
the parameter (testsuite vs. test suite).

lib/phpunit/classes/util.php

@@ -435,7 +435,7 @@ class phpunit_util extends testing_util {
         global $CFG;
 
         $template = '
-        <testsuite name="@component@ test suite">
+        <testsuite name="@component@_testsuite">
             <directory suffix="_test.php">@dir@</directory>
         </testsuite>';
         $data = file_get_contents("$CFG->dirroot/phpunit.xml.dist");