Move set nonce / set length tests to positive test
Move set nonce / set length tests to positive test

Previous test in state test was not actually making sure that the
operatioon could be completed using set lengths / set nonce in either
order, thus changed the 'normal' encrypt / decrypt tests to run in
alternating order.

Signed-off-by: Paul Elliott <c95151bd40fac1aa138ed1651e2873f91d2e1899@arm.com>

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