Fix problem found with host bionic fortify checks

hardware/interfaces/bluetooth/1.0/default/test/bluetooth_address_test.cc:59:39:
error: 'open' called with O_CREAT or O_TMPFILE, but missing mode

Bug: 31559095
Test: out/host/linux-x86/nativetest{,64}/bluetooth-address-unit-tests/bluetooth-address-unit-tests
Change-Id: I913c78e25eccaecf8830f1caf8e92f834ab8bb76