PathClassLoaderTest: add test about loading resources with tampered certificates

Document that classloading with malformed certificates succeed, although
the call to getCertificates returns null.

hyts_signed_wrong_cert.jar was obtained by taking
hyts_signed.jar and changing META-INF/TEST.DSA by deleting
the first byte.

Bug: 27826114
Change-Id: Ia088d4ef0247a28bebf7ea66977a29afb2ca40ee