lint-hunks: exit status for only affected lines

Prior to this patch, if there were any lint errors, this script would
exit with an error, even if those errors were not in the hunks being
tested by this script. This change makes it so that if any lint lines
are printed, an error is returned.

Change-Id: I69c8bef4367ccf25d287508f29e587b1f4426143

tools/lint-hunks.py

@@ -111,8 +111,6 @@ def main(argv=None):
             lint = Subprocess(cpplint_cmd, expected_returncode=(0, 1),
                               stdin=show.stdout, stderr=subprocess.PIPE)
             lint_out = lint.communicate()[1]
-            if lint.returncode == 1:
-                lint_failed = True
 
             for line in lint_out.split("\n"):
                 fields = line.split(":")
@@ -122,8 +120,9 @@ def main(argv=None):
                 if warning_line_num in affected_lines:
                     print "%s:%d:%s"%(filename, warning_line_num,
                                       ":".join(fields[2:]))
+                    lint_failed = True
 
-        # Propagate lint's exit status
+        # Set exit code if any relevant lint errors seen
         if lint_failed:
             return 1