rootfs_ipk, package_ipk: drop --force-overwrite

rootfs_ipk, package_ipk: drop --force-overwrite

* it was introduced in 2010 by 8c3a7ebac8bed700bcc37f778d5a883cfeee8de8
  but doesn't seem needed anymore
* also such do_rootfs failure is good indication that runtime packages
  installed are not sane, ignoring this error in do_rootfs just
  transfers the issue to end user when he does "opkg upgrade" later
  on device
* tested on SHR images with whole feed included and only issue was
  gstreamer/gst-plugins-* locale packages (and there is patch for this
  on oe-core ML)

(From OE-Core rev: 1f7d3a2e9071ff78170c06ebf58c7400a5ee09bf)

Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com>
Signed-off-by: Saul Wold <sgw@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>