dependencies: Downgrade pika to avoid constantly logged errors.

With the new pika 0.11.2, we got a lot of errors from pika on
chat.zulip.org.  See #8466 for details.

requirements/common.in

@@ -95,7 +95,7 @@ oauthlib==2.0.6
 ndg-httpsclient==0.4.4
 
 # Needed to access rabbitmq
-pika==0.11.2
+pika==0.11.0
 
 # Needed to access our database
 psycopg2==2.7.3.2

requirements/dev.txt

@@ -99,7 +99,7 @@ pbr==3.1.1                # via mock
 pexpect==4.3.0            # via ipython
 phonenumberslite==8.8.6   # via django-phonenumber-field
 pickleshare==0.7.4        # via ipython
-pika==0.11.2
+pika==0.11.0
 pillow==5.0.0
 pip-tools==1.11.0
 polib==1.1.0

requirements/prod.txt

@@ -69,7 +69,7 @@ pbr==3.1.1                # via mock
 pexpect==4.3.0            # via ipython
 phonenumberslite==8.8.6   # via django-phonenumber-field
 pickleshare==0.7.4        # via ipython
-pika==0.11.2
+pika==0.11.0
 pillow==5.0.0
 polib==1.1.0
 premailer==3.1.1

version.py

@@ -8,4 +8,4 @@ ZULIP_VERSION = "1.7.1+git"
 # Typically, adding a dependency only requires a minor version bump, and
 # removing a dependency requires a major version bump.
 
-PROVISION_VERSION = '14.12'
+PROVISION_VERSION = '15.0'