[lldb-dap] Improving stability of TestDAP_launch_commands. (#179783)

Improving stability of the TestDAP_launch_commands test.

When collecting output for verifying 'stopCommands' we were not waiting
for the output to finish, which could cause issues if the test is
running very fast.

GitOrigin-RevId: 35ada11f1b4b9ca51f8b07af4cc9a7aa3400028e
1 file changed