TESTS: replace read* flags tests with dedicated dpo/fua tests

Remove the flags tests for READ* and replace them with a test for the DPO
and FUA bits.
IF the device claims DPOFUA support in modesense then the READ* CDBs
MUST allow these two flags. IF the device does NOT claim DPOFUA then any
READ* CDB with these flags must fail with invalod field in cdb.

Signed-off-by: Ronnie Sahlberg <ronniesahlberg@gmail.com>