Replace hard-coded install paths

:Release Notes:
Now luna-sysservice takes into account actual installation prefix of
webOS

:Detailed Notes:
Replaced hard-coded paths with equivalents based on appropriate
parameters of build configuration.

:Testing Performed:
Desktop build with webOS install prefix set to /opt/webos

:QA Notes:

:Issues Addressed:

Open-webOS-DCO-1.0-Signed-off-by: Nikolay Orliuk <nikolay.orliuk@lge.com>
Change-Id: I2e8af4f4fa39c000bd8d2924815aa9999011efa3
Reviewed-on: https://g2g.palm.com/3593
Reviewed-by: Keith Derrick <keith.derrick@lge.com>
Tested-by: Keith Derrick <keith.derrick@lge.com>