Longer timeouts in package_json_changes test
Longer timeouts in package_json_changes test

Summary:
There were some reports of flakiness in package_json_test. Mostly the tests passed. But occasionally we saw failures, sometimes of test 2, sometimes of test 3. Here's test 2:
```
test('haste - Adding a package.json should kill the server', [
  addFile('start.json', 'package.json')
    .waitForServerToDie(2000)
    .verifyServerStatus('stopped')
]).flowConfig('haste_flowconfig'),
```
When it failed, the logs looked like this:
```
Actual 'server is running' (+) didn't match expected 'server is running' (-)
+ running
- stopped
STEP 1
Running force-recheck for files: package.json
force-recheck finished
```

What was happening? My guess is that the test machine was just under heavy load and it didn't yet get around to terminating the server after the force-recheck had finished.

Indeed, if I changed the timeout from 2s down to 1s, then the tests reliably fail with the same error message!

So I've bumped the timeout up to 10s.

Reviewed By: mroch

Differential Revision: D7806973

fbshipit-source-id: eb9081219ccb4b7e722feeb5f14c6d35e938131d

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