Revert "Lazily preload secondary zygote resources."

This reverts commit e5aee79e.

Given recent improvements to boot timing, and higher paralellization,
the lazy preloading of zygote resources makes boot time slightly slower
by ~100-250ms. Therefore, the change is being reverted until we can do
it properly and defer it to a later point in the boot process. This work
is being tracked by b/34810190

BEFORE
------
successive-online : 17290.0,17633.0,17329.0,17655.0,16802.0,16888.0,17645.0,17369.0,17572.0,16932.0,
successive-online_avg : 17311.5
successive-boot : 24834.0,25119.0,25122.0,25091.0,25617.0,25535.0,25047.0,27462.0,25088.0,25648.0,
successive-boot_avg : 25456.3

AFTER
-----
successive-online : 16973.0,16530.0,17015.0,17953.0,17367.0,17098.0,16887.0,17377.0,18039.0,16742.0,
successive-online_avg : 17198.1
successive-boot : 24921.0,25622.0,25781.0,25449.0,25128.0,24774.0,24554.0,25029.0,24544.0,25809.0,
successive-boot_avg : 25161.1

Test: Boot timings collected with tradefed harness.
Bug: 34810190
Change-Id: I9a6dd5ce31bda067e74fc088b057711fa4a7a0fb