Releng: Update Maven findbugs, jacoco and jarsigner to support Java 8

See https://bugs.eclipse.org/bugs/show_bug.cgi?id=457949



Change-Id: I91b51bf4ed4a2adbd4b31566343b3e701c161c52
Signed-off-by: Martin Oberhuber <mober.at+eclipse@gmail.com>