Fix pre-release target SDK APEX failure test

With a fix in the platform, sessions will now fail at commit time
rather than at install time. Adds assertFailure which checks for this.

Bug: 184942889

Test: atest com.android.tests.stagedinstall.host.StagedInstallTest
        #testApexTargetingOldDevSdkFailsVerification

Merged-In: I7e6c199083f3ba31e6baed646dbc7ac2ae7c86e4
Change-Id: I7e6c199083f3ba31e6baed646dbc7ac2ae7c86e4
2 files changed