Added fix required to run on Ubuntu 14.04

When run with the NeCTAR Ubuntu 14.04 image the pip install of
the requirements.txt file fails because:

* pbr is already installed, and is an earlier version that that required
* there are other python packages required that are not installed.

This fix uses pip to upgrade the pbr version installed, and adds
the required packages to the requirments.txt file.

Closes-Bug: #1636150
Change-Id: I2b5a3988cfbaa1c2b6feec0a3e18dec805fcfb83

contrib/install.sh

@@ -129,6 +129,8 @@ if [[ -e /etc/os-release ]]; then
 
         git clone https://git.openstack.org/openstack/faafo
         cd faafo
+        # following line required by bug 1636150
+        sudo pip install --upgrade pbr
         sudo pip install -r requirements.txt
         sudo python setup.py install
 

requirements.txt

@@ -1,4 +1,7 @@
 pbr>=1.6
+pytz
+positional
+iso8601
 anyjson>=0.3.3
 eventlet>=0.17.4
 PyMySQL>=0.6.2,<0.7  # 0.7 design change breaks faafo, MIT License