[+BUGFIX] FLOW3 (Testing): Use better uniqid() in ObjectManagerTest
On Windows successive calls of the PHP function uniqid() seem to create the
same string in certain circumstances.
In the ObjectManagerTest we use uniqid() to create mock class names.
This leads to a fatal error in about every fifth execution of the testrunner on
This is fixed by specifying the "more_entropy" parameter and prefixing the
id with a random number.