webos_system_bus: Don't stage service and role files

:Release Notes:
When there are multiple providers for the same service built in the
same sysroot (but in the end included in different images) bitbake
shows warnings. Silence them by removing service and role files from
staging. Also remove luna-service2 runtime dependency.

:Detailed Notes:
Some allarch recipes inherit webos_system_bus, but luna-service2 isn't
allarch, so the runtime dependency was tainting their signature.

:Testing Performed:
Build tested and checked that the same service and role files are still
installed in image, while corresponding directories in sysroot are
empty.

:QA Notes:
No change in image.

:Issues Addressed:
[GF-40567] Disable installing LS2 service and role files in the target
           sysroot

Open-webOS-DCO-1.0-Signed-off-by: Martin Jansa <martin.jansa@lge.com>
Change-Id: I655d0b0258893c11bdf1e818123d0d5a734aa6b9
Reviewed-on: https://g2g.palm.com/3572
Reviewed-by: Herb Kuta <herb.kuta@lge.com>
Tested-by: Herb Kuta <herb.kuta@lge.com>
Reviewed-by: Build Verification
Reviewed-by: Jongho Kim <jongho1208.kim@lge.com>
Tested-by: Jongho Kim <jongho1208.kim@lge.com>