[BUGFIX] Fix failing PHPUnit-Tests on Windows due to uniqid()-calls

If in one test multiple objects are created and their names are created
with uniqid()-calls without params, they fail because they return the
same value.

Using md5(uniqid(microtime(), true)) instead makes object names unique.

Resolves: #63943
Releases: master, 6.2
Change-Id: Ib223d45f04946223c4a8ae9ce68a5c5b24459355
Reviewed-on: http://review.typo3.org/35529
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>