When a Java 8 JVM is launched with -XX:MaxPermSize a warning message
is output indicating that the option will be ignored. This causes the
CLI tests that assert that no error output has been produced to fail.

This commit updates the CLI's integration test harness to remove
JAVA_OPTS from the environment of the CLI process. This prevents any
unwanted max perm size configuration from leaking into that
environment and breaking the build.