Keystore CTS: allow for rounding in creation time

Some devices appear to round timestamps to the nearest second; relax the
comparison vs "now" to allow for this.

Bug: 230396203
Test: atest CtsKeystoreTestCases:android.keystore.cts.KeyAttestationTest
Change-Id: I8f792e3202a6d0d3b4afbf4dcc00b238490d48f2
1 file changed