[Fix] Update AbstractSamplesTest to properly handle base directories with special characters (e.g. spaces)

[er1c]

The getFile here is returning a String that is potentially adding escaping characters (e.g. '%20'). The java.ioFile can natively take a URI as a parameter, so avoid trying to convert the path to a string, and simply avoid the issue.

[INFO] JAXB2 Basics - Project ............................. SUCCESS [  0.129 s]
[INFO] JAXB2 Basics - Ant Task ............................ SUCCESS [  3.454 s]
[INFO] JAXB2 Basics - Runtime ............................. SUCCESS [  6.756 s]
[INFO] JAXB2 Basics - Tools ............................... SUCCESS [  3.976 s]
[INFO] JAXB2 Basics - Testing ............................. SUCCESS [  3.436 s]
[INFO] JAXB2 Basics - Basic Plugins ....................... SUCCESS [  3.529 s]
[INFO] JAXB2 Basics - Full Plugins JAR .................... SUCCESS [  0.375 s]
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[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 21.843 s
[INFO] Finished at: 2019-01-12T16:11:09+00:00
[INFO] Final Memory: 23M/291M
[INFO] ------------------------------------------------------------------------