Update the reference profile from .dm files only during installs

In order to speed up first boot time we only create the current profile
and do not update the content of the reference profile. A system image
should already be configured with the right profile keys and the
profiles for the speed-profile prebuilds should already be copied (that's
done in #performDexOptUpgrade).

Test: manual (install apps and splits, take OTA)
Bug: 114046578
Change-Id: I99db76684430b929c52634c25b457e874648e205