Problem:
========
- After the commit ada1074b (MDEV-14398)
fil_crypt_set_encrypt_tables() iterates through all tablespaces to
fill the default_encrypt tables list. This was a trigger to
encrypt or decrypt when key rotation age is set to 0. But import
tablespace does call fil_crypt_set_encrypt_tables() unnecessarily.
The motivation for the call is to signal the encryption threads.

Fix:
====
ha_innobase::discard_or_import_tablespace: Remove the
fil_crypt_set_encrypt_tables() and add the import tablespace
to the default encrypt list if necessary