Don't write nonexistent DEX file paths to dexpreopt.config files.

A path to an nonexistent file caused dex2oat to write an empty path in
the class loader context stored inside of the OAT/ODEX file, which
resulted in class loader context mistmatch and a failure to load
dexpreopt code on device.

An example of a faulty class loader context for GoogleDialer, can be
seen either with oatdump or by grepping logcat for class loader context
mimatch messages (the first empty PCL[] is expected, note the second
empty PCL[] in the subcontext for shared libraries):

  PCL[]{PCL[]#PCL[/system/framework/org.apache.http.legacy.jar*22205474]

This CL removes the nonexistent path from the generated dexpreopt.config
file, which works in conjunction with a change in makefiles that stops
using the removed config field. This is possible because makefiles can
access DEX files using a module name and "intermediates-dir-for" macro.

Bug: 132357300
Test: lunch cf_x86_64_phone-userdebug && m && launch_cvd \
      adb wait-for-device && adb root && adb logcat \
      | grep -E 'ClassLoaderContext [a-z ]+ mismatch'
      # empty grep output, no errors
Change-Id: I8d16f77c6f76ad6234cc4114ad3545cbe572ef13