[DexManager] Fix off-by-N error in DexManager when reporting dex loads

In this loop the continue statement skips over incrementing
dexPathIndex. In effect the classloader context that reported for a
given dex file may be incorrect (specifically in the situation when the
user loads a primary dex file and a secondary dex file in the same
ClassLoader)

Bug: 147089377
Test: atest com.android.server.pm.dex.DexManagerTests
Change-Id: I7d3df507787f758537625b702131a2f4f76190e6