DLPX-85513 savedump: Fix Bogus Warning About Missing Debug Info (#15)

While trying to archive a userland core dump for SDB's regression suite
I came across this minor bug where files that already had debug info
were raising errors that they don't have any, like this:
```
warning: could not find debug info of: /export/home/delphix/zfs/.libs/ztest
warning: could not find debug info of: /export/home/delphix/zfs/lib/.libs/libzpool.so.5
warning: could not find debug info of: /export/home/delphix/zfs/lib/.libs/libnvpair.so.3
```

These files were added to the crash dump regardless but the above output
is misleading. This patch fixes the issue.

savedump/savedump.py

@@ -422,7 +422,7 @@ def binary_includes_debug_info(path: str) -> Optional[bool]:
         if '.debug_str' in line:
             debug_str = True
         if debug_info and debug_str:
-            return False
+            return True
     return False