work around for packaging problem with python-glanceclient-0.5.1 in epel

python-glanceclient-0.5.1 from epel has a requirements.txt file that has a hard dependency on python-keystoneclient>=0.1.2,<0.2
The latest version of python-keystoneclient in epel is 0.2, so this breaks the glanceclient dependency.  Until the bug is fixed, we can just remove the requirements.txt file as it doesn't play nicely (and isn't needed) when working with RPMs which have their own dependency framework.