Import operation without .cfg file fails when there is mismatch of index
between metadata table and .ibd file. Moreover, MDEV-19022 shows
that InnoDB can end up with index tree where non-leaf page has only
one child page. So it is unsafe to find the secondary index root page.

This patch does the following when importing the table without .cfg file:

1) If the metadata contains more than one index then InnoDB stops
the import operation and report the user to drop all secondary
indexes before doing import operation.

2) When the metadata contain only clustered index then InnoDB finds the
index id by reading page 0 & page 3 instead of traversing the
whole tablespace.