Fix some tests.

- JavaAPISuite was trying to compare a bare path with a URI. Fix by
  extracting the path from the URI, since we know it should be a
  local path anyway/

- b9be1609 excluded the ASM dependency everywhere, but easymock needs
  it (because cglib needs it). So re-add the dependency, with test
  scope this time.

The second one above actually uncovered a weird situation: the maven
test target works, even though I can't find the class sbt complains
about in its classpath. sbt complains with:

  [error] Uncaught exception when running org.apache.spark.util
  .random.RandomSamplerSuite: java.lang.NoClassDefFoundError:
  org/objectweb/asm/Type

To avoid more weirdness caused by that, I explicitly added the asm
dependency to both maven and sbt (for tests only), and verified
the classes don't end up in the final assembly.

Author: Marcelo Vanzin <vanzin@cloudera.com>

Closes #917 from vanzin/flaky-tests and squashes the following commits:

d022320 [Marcelo Vanzin] Fix some tests.