Fix TestAttachResume test so it doesn't hang on Linux with ptrace lockdown.

Similar to previous fix, this augments the test inferior to
immediately indicate it may be ptraced by any Linux process
when the appropriate symbols are defined.

This seems to indicate we need to fix our lldb attach logic to
catch when an attach fails, and trigger an appropriate error
instead of the current behavior of hanging indefinitely.

llvm-svn: 220654