Fixes support for passing arguments to klee in the ConcreteTests.

This is for use with llvm-lit --param=klee_opts=...

Fixes lit.cfg to not have an extraneous space behind the klee command.
Augments ConcreteTest to accept and pass arguments to klee.
Augments all the ConcreteTest cases to wrap %klee in quotes.

Without wrapping %klee the extra arguments will be seen as arguments
to ConcreteTest.py resulting in an unknown argument error.