Do export sanity checks in import_export as well
Do export sanity checks in import_export as well

This is not useful to validate the implementation when importing
canonical input, which is the case for most import/export test cases,
but it helps validate the sanity checks themselves.

NXPmicro/mbedtls,NXPmicro/mbedtls,ARMmbed/mbedtls,ARMmbed/mbedtls,NXPmicro/mbedtls,Mbed-TLS/mbedtls,NXPmicro/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls,Mbed-TLS/mbedtls