Update unit tests to be compatiable with PHPUnit6&7

phpunit.xml.dist

 <?xml version="1.0"?>
-<phpunit backupGlobals="false" backupStaticAttributes="false" colors="true" convertErrorsToExceptions="true" convertNoticesToExceptions="true" convertWarningsToExceptions="true" processIsolation="false" stopOnFailure="false" syntaxCheck="false" bootstrap="tests/phpunit/bootstrap.php">
+<phpunit backupGlobals="false" backupStaticAttributes="false" colors="true" convertErrorsToExceptions="true" convertNoticesToExceptions="true" convertWarningsToExceptions="true" processIsolation="false" stopOnFailure="false" bootstrap="tests/phpunit/bootstrap.php">
   <testsuites>
     <testsuite name="My Test Suite">
       <directory>./tests/phpunit</directory>

tests/phpunit/api/v3/Job/MosaicoMsgSyncTest.php

@@ -10,7 +10,7 @@ use CRM_Mosaicomsgtpl_ExtensionUtil as E;
  * This is a generic test class implemented with PHPUnit.
  * @group headless
  */
-class api_v3_Job_MosaicoMsgSyncTest extends \PHPUnit_Framework_TestCase implements HeadlessInterface, HookInterface, TransactionalInterface {
+class api_v3_Job_MosaicoMsgSyncTest extends \PHPUnit\Framework\TestCase implements HeadlessInterface, HookInterface, TransactionalInterface {
 
   /**
    * Civi\Test has many helpers, like install(), uninstall(), sql(), and sqlFile().