Otadexopt: Attempt to mount product partition

Attempt to mount the product partition to give postinstall dexopt
access to those APKs.

(cherry picked from commit b87a1c79)

Bug: 78032768
Test: m
Test: manual
Merged-In: Ic74e2580a01d0fba3e217158e0d50ba1270f7806
Change-Id: Ic74e2580a01d0fba3e217158e0d50ba1270f7806