iorap: Change the init config of iorapd.

Only start iorapd when either prefetching or tracing is enabled.

Bug: 176037717
Test: atest CtsStagedInstallHostTestCases:
com.android.tests.stagedinstall.host.StagedInstallTest#testInstallStagedApexAndApk

Change-Id: Iea419aa40124e79595d4f4da35c4856a9fdc9608
1 file changed