Correct the keystore alias used for secure imports

An Android-O timeframe refactor removed all use of keystore "skey"
aliases.  Creating one not only partially reverses that refactor, but
it also results in a key alias which cannot be deleted in some cases,
causing AndroidKeyStoreTest failures during the second run of CTS.

Bug: 80228327
Test: CTS tests ImportWrappedKeyTest and AndroidKeyStoreTest, in that order
Change-Id: I348ba421f29cdf6c65fc98be3a25d19938d559c1