Fall back to "copy" strategy if linking throws an EAGAIN error (#338)

add EAGAIN to list of handled errors

Author: mermerico

src/dvc_objects/fs/generic.py

@@ -299,6 +299,7 @@ def _try_links(
                 errno.ENOTTY,
                 errno.ENOSYS,
                 errno.EINVAL,
+                errno.EAGAIN,
             ):
                 raise
             error = exc