Modify process start position to proper signal

:Release Notes:
- Modify process start position to proper signal

:Detailed Notes:
'boot-phase2-complete' is finally dropped.
BootD generates 'minimal-boot-done' upstart signal
when core services are ready. (SAM, Showcase and network)
Therefore, we need to use 'minimal-boot-done'.

:Testing Performed:

:QA Notes:

:Issues Addressed:
[GF-35147] [Boottime] Make best boot sequence to support showcase-app
           initialization

Open-webOS-DCO-1.0-Signed-off-by: Sangwoo Kang <sangwoo82.kang@lge.com>

Change-Id: I229ce336aa3db5a442874ffd0b5895fa4bb5fabc
Reviewed-on: https://g2g.palm.com/3400
Reviewed-by: Build Verification
Reviewed-by: Sangwoo Kang <sangwoo82.kang@lge.com>
Tested-by: Sangwoo Kang <sangwoo82.kang@lge.com>
Reviewed-by: Ed Chejlava <ed.chejlava@lge.com>
Reviewed-by: Roger Stringer <roger.stringer@lge.com>