CertificateTest: explicitly set validity check date

Since this test uses pre-generated certificates, they will expire
eventually given enough time. Instead of regenerating them, just set the
date in the PKIXParameters to compare their validity against.

(cherry picked from commit 4412830e)

Test: vogar --mode host --classpath out/host/common/obj/JAVA_LIBRARIES/core-tests-support-hostx_intermediates/classes.jack --classpath out/host/common/obj/JAVA_LIBRARIES/core-tests-hostdex_intermediates/classes.jack libcore/luni/src/test/java/tests/targets/security/cert/CertificateTest.java
Bug: 32756119
Bug: 32767302
Change-Id: Id48ecf289277ae9d98642b15aaa17c126bdc43e9