This patch fixes a bug in dotest.py where lldb.selected_platform was
being set to host platform even after a successful connection to a
remote platform via platform url. This patch fixes this behavior and
sets selected_platform to remote_platform after a successful connection.
This patch also removes target_platform variable from run_suite.
Reviewed By: JDevlieghere
Differential Revision: https://reviews.llvm.org/D105060