contrib: make import-checker agree more with run-tests about heredocpy

run-tests.py and import-checker.py take wholly different approaches to
.t-tests, and the result was that they had different notions about
when a Python heredoc had ended, leading to conflicts. This resolves
part of the issue, and the rest I can deal with by tweaking the one
offending test file.

contrib/import-checker.py

@@ -693,7 +693,10 b' def embedded(f, modname, src):'
             else:
                 script.append(l[4:])
             continue
-        if inlinepython and l == b'  \n':
+        # If we have an empty line or a command for sh, we end the
+        # inline script.
+        if inlinepython and (l == b'  \n'
+                             or l.startswith(b'  $ ')):
             yield b''.join(script), (b"%s[%d]" %
                    (modname, inlinepython)), t, inlinepython
             script = []