test: test-crypto-classes timeout on Raspberry Pi

[BridgeAR]

This timed out multiple times on Raspberry Pi. Ping @bengl

https://ci.nodejs.org/job/node-test-binary-arm/10431/RUN_SUBSET=3,label=pi2-raspbian-wheezy/console
https://ci.nodejs.org/job/node-test-binary-arm/10437/RUN_SUBSET=3,label=pi3-raspbian-jessie/console
https://ci.nodejs.org/job/node-test-binary-arm/10430/RUN_SUBSET=6,label=pi1-raspbian-wheezy/console

not ok 42 parallel/test-crypto-classes
  ---
  duration_ms: 240.40
  severity: fail
  stack: |-
    timeout

[bengl]

It turns out the test does take some time. I'm investigating.

[mhdawson]

Failures here as well:

https://ci.nodejs.org/job/node-test-binary-arm/10479/RUN_SUBSET=3,label=pi1-raspbian-wheezy/console
https://ci.nodejs.org/job/node-test-commit-arm/12387/nodes=armv7-wheezy/