Remove PyKafka from global-requirements

PyKafka was added to g-r as planned replacement for kafka-python client
in Monasca [1]. Support for this client was never added though and the
library is not used. Recent tests have shown that confluent-kafka client
provides better throughtput and Kafka API support. Current plan is to
add support for confluent-kafka client in Monasca instead of PyKafka
[2].

No other project uses PyKafka [3].

[1] https://git.openstack.org/cgit/openstack/requirements/commit/?id=c1749152a85a80180198a5985d34d3ab86aeb722
[2] https://storyboard.openstack.org/#!/story/2003079
[3] http://codesearch.openstack.org/?q=pykafka&i=nope&files=&repos=

Depends-On: https://review.openstack.org/585374
Change-Id: I91202fc1187c284c0fd994ad7d8bd649f5973196

global-requirements.txt

@@ -205,7 +205,6 @@ PyECLib  # BSD
 pyghmi  # Apache-2.0
 pyinotify;sys_platform!='win32' and sys_platform!='darwin' and sys_platform!='sunos5'  # MIT
 PyJWT  # MIT
-pykafka  # Apache 2.0 License
 pykmip  # Apache 2.0 License
 python-ldap  # PSF
 pylxd  # Apache-2.0

openstack_requirements/tests/files/upper-constraints.txt

@@ -367,7 +367,6 @@ six===1.10.0
 h2===2.6.0;python_version=='3.4'
 h2===2.6.0;python_version=='3.5'
 dulwich===0.17.1
-pykafka===2.5.0
 kombu===4.0.1
 yaql===1.1.3
 requestsexceptions===1.2.0

upper-constraints.txt

@@ -428,7 +428,6 @@ python-memcached===1.59
 openstacksdk===0.17.2
 six===1.11.0
 dulwich===0.19.6
-pykafka===2.7.0
 kombu===4.2.1
 distro===1.3.0
 betamax-matchers===0.4.0