Disable sdcardfs from emulated_stroage.mk

This sets external_storage.sdcardfs.enabled=0 from emulated_storage.mk,
which will disable sdcardfs on devices that are using casefolding and
quotas as sdcardfs replacements. This allows the device to use these if
sdcardfs is present in the kernel.

Bug: 155222498
Test: mount|grep "type sdcardfs" should find nothing after boot complete
      if external_storage.sdcardfs.enabled=0
Change-Id: Id0446a7cac5ac768afc3b3e046359fc4e945e554