mediaserver : Initialize ICU on startup.

In change 2b29e461c in external/icu, we stopped hardcoding the ICU
data path at compile time to avoid two sets of mappings in zygote forked
processes. This means we'll have to tell ICU where its data is if the
process in question isn't forked from the zygote.

bug: 21705078
Change-Id: I829d9fa34fe8209aa8a6d55145ca26fdf0d934e8