test_that_stbt_control_sends_a_single_key: Don't print NullRemote message twice

The output from "tests/run-tests -v test_that_stbt_control_sends_a_single_key"
was confusing because it looked like "stbt control" had called
"stbt.press" *twice*, when really the second time was printed by the
"grep" command.
stbt control: Fix pep8 indentation errors

stbt-control:192:9: E128 continuation line under-indented for visual indent
stbt-control:254:9: E128 continuation line under-indented for visual indent