(maint) Upgrade netty development dependency
(maint) Upgrade netty development dependency

We get netty 3.9.2.Final as a transitive dependency of [http.async.client
"0.6.1"], but 3.9.9.Final is available and has a few commits that would appear
to address websockets races that are causing instability in the
puppetlabs.pcp.broker.service-test/it-expects-ssl-client-auth-test test:

https://github.com/netty/netty/compare/3ca6c4d9385134d730567a932812c281d772f320...22fcfe7c94c722842f491448a38b5078caf1d417

Updating this dependency doesn't completely fix the problem, but
it seems to reduce its rate of occurance:

    [vagrant@localhost pcp-broker]$ lein test :only puppetlabs.pcp.broker.service-test/it-expects-ssl-client-auth-test

    lein test puppetlabs.pcp.broker.service-test

    Ran 1 tests containing 1 assertions.
    0 failures, 0 errors.
    [vagrant@localhost pcp-broker]$ lein test :only puppetlabs.pcp.broker.service-test/it-expects-ssl-client-auth-test

    lein test puppetlabs.pcp.broker.service-test

    Ran 1 tests containing 1 assertions.
    0 failures, 0 errors.
    [vagrant@localhost pcp-broker]$ lein test :only puppetlabs.pcp.broker.service-test/it-expects-ssl-client-auth-test

    lein test puppetlabs.pcp.broker.service-test

    Ran 1 tests containing 1 assertions.
    0 failures, 0 errors.

    [vagrant@localhost pcp-broker]$ uname -a
    Linux localhost.localdomain 3.10.0-123.20.1.el7.x86_64 #1 SMP Thu Jan 29 18:05:33 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
    [vagrant@localhost pcp-broker]$ java -version
    java version "1.7.0_91"
    OpenJDK Runtime Environment (rhel-2.6.2.1.el7_1-x86_64 u91-b00)
    OpenJDK 64-Bit Server VM (build 24.91-b01, mixed mode)

vs:

    $ lein test :only puppetlabs.pcp.broker.service-test/it-expects-ssl-client-auth-test

    FAIL in (it-expects-ssl-client-auth-test) (service_test.clj:78)
    Disconnected due to no client certificate
    expected: (= [4003 "No client certificate"] (deref closed (* 2 1000) false))
      actual: (not (= [4003 "No client certificate"] [1006 "Connection was closed abnormally (that is, with no close frame being sent)."]))

puppetlabs/pcp-broker,puppetlabs/pcp-broker,puppetlabs/pcp-broker