Fix whitespace in the python test suite.

Summary:
The test suite has often unnecessary trailing whitespace, and sometimes
unnecessary trailing lines or a missing final new line. This patch just strips
trailing whitespace/lines and adds missing newlines at the end.

Subscribers: ki.stfu, JDevlieghere, christof, lldb-commits

Differential Revision: https://reviews.llvm.org/D49943

llvm-svn: 338171