Backport "Ensuring .writable_image is erased on format data"

* commit 436c294494139ce2ee8d8269019459a5b0f398a4

  Ensuring .writable_image is erased on format data

  The /data/* doesn't pickup hidden files; explicitly selecting
  .writable_image

  Change-Id: I84be2e64b93381eb995a0e191e2e700d8c78bccf
  Signed-off-by: Sergio Schvezov <sergio.schvezov@canonical.com>

Change-Id: I6020979428bd24beb22adae3838cf89ae6553f49