Check key store result with isOk() instead of casted value

The underlying value of the return code is not meaningful
in a check, instead isOk() should be used.

Bug: 119771891
Test: Built for walleye successfully, basic operations with
      keystore_cli_v2 tool work correctly, new cts test
      no longer finds a crash in keystore.
Change-Id: Id20612824677619cbbd0b2ba4a11b15fe5258ecb
1 file changed