main: Simplify version handling

Print a simple version string rather than delaying the output
to display a structured version string. The structured output
is potentially more useful but:

- This output is not consistent with other components.

- Delaying the output makes `--version` unusable in some
  environments (since a lot of setup is called before the
  version string can be output).

Signed-off-by: James O. D. Hunt <james.o.hunt@intel.com>

src/agent/src/main.rs

@@ -105,6 +105,19 @@ fn announce(logger: &Logger) {
 
 fn main() -> Result<()> {
     let args: Vec<String> = env::args().collect();
+
+    if args.len() == 2 && args[1] == "--version" {
+        println!(
+            "{} version {} (api version: {}, commit version: {}, type: rust)",
+            NAME,
+            version::AGENT_VERSION,
+            version::API_VERSION,
+            env::var("VERSION_COMMIT").unwrap_or("unknown".to_string())
+        );
+
+        exit(0);
+    }
+
     if args.len() == 2 && args[1] == "init" {
         rustjail::container::init_child();
         exit(0);
@@ -177,13 +190,6 @@ fn main() -> Result<()> {
 
     announce(&logger);
 
-    if args.len() == 2 && args[1] == "--version" {
-        // force logger to flush
-        drop(logger);
-
-        exit(0);
-    }
-
     // This "unused" variable is required as it enables the global (and crucially static) logger,
     // which is required to satisfy the the lifetime constraints of the auto-generated gRPC code.
     let _guard = slog_scope::set_global_logger(logger.new(o!("subsystem" => "rpc")));