service_contexts: strip blank lines and comments

Strip whitespace and comments from service_context files
to reduce size. On an aosp_x86_64 build it saves 36 bytes.

However, on builds with more synclines and comments, further
space savings can be realized.

Change-Id: I3cb4effad1d1b404bf53605a3793e3070cb95651
Signed-off-by: William Roberts <william.c.roberts@intel.com>