Install a known working recent version of pip that handles installation
dependencies more correctly than before. Extract to a separate script
so it can be used apart from stack.sh.
* Install distro setuptools if it not already present
* Install pip from source tarball as get-pip.py proved to be unreliable
* Remove python-distribute and python-pip from all prereq files,
move python-setuptools to 'general'
* Remove the earlier unfubar_setuptppls() call that attenpted to fix this
* Only update requirements.txt when no changes in repo
Tested on Precise, F18 and CentOS6.
* Fedora and RHEL allow pip to install packages ON TOP OF RPM-installed
packages. THIS IS BROKEN. And is one reason we have to be so picky
about order and so forth.
Change-Id: Ibb4b42119dc2e51577c77bbbbffb110863e5324d
62d1d698a0