Fix build of agl-demo-image-qa

Fix build of agl-demo-image-qa

Fix the image generation by fixing SPEC-782,
updating iperf and removing our custom version of ltp
in favour of a newer version in oe-core.

Bug-AGL: SPEC-782

Change-Id: Idbb08b493645f04df3d04c93d7bef8231350078d
Signed-off-by: Jan-Simon Möller <jsmoeller@linuxfoundation.org>
Reviewed-on: https://gerrit.automotivelinux.org/gerrit/10367
Tested-by: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>
ci-image-build: Jenkins Job builder account <agl-jobbuilder@automotivelinux.org>