refactor metadata pack/unpack functions

Move the `parse` and `combine` functions, which are used to translate
between `map<string,string>` and `vector<string>` for the metadata.
This is in preparation for transitioning the AdditionalData field
from `vector` to `map`.

Tested: Test cases pass.  Simple `log-create` call has no change in
behavior.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ib968e1fe02903072c300d5387cf91f2d8164b1b4
diff --git a/phosphor-rsyslog-config/meson.build b/phosphor-rsyslog-config/meson.build
index a24baf9..4d85b20 100644
--- a/phosphor-rsyslog-config/meson.build
+++ b/phosphor-rsyslog-config/meson.build
@@ -2,6 +2,7 @@
     'main.cpp',
     'server-conf.cpp',
     '../elog_meta.cpp',
+    '../util.cpp',
     elog_process_gen,
     include_directories: include_directories('..'),
     dependencies: [