main: Fix error propagation if starting the VM fails

Commit 21d40d7 ("main: reset tty if starting the VM fails") changed
start_vmm() to join the vmm thread if an error happens after the vmm
thread is started. The implementation put all the error-prone code that
is run after the vmm is started in a closure, to be able to always join
the vmm thread, regardless of any error happening. However, it missed
propagating the error that might happen inside the closure back to the
main function, after joining the vmm thread.

For some cmd line options, the above issue inhibits proper error
reporting when starting a VM with invalid commands, as many parameters
are parsed after the vmm is started, thus if such parsing fails, no
error will be reported back to the user.

See: #5435
Fixes: 21d40d7 ("main: reset tty if starting the VM fails")
Signed-off-by: Rafael Mendonca <rafaelmendsr@gmail.com>

src/main.rs

@@ -573,7 +573,7 @@ fn start_vmm(toplevel: TopLevel) -> Result<Option<String>, Error> {
         .map_err(Error::ThreadJoin)?
         .map_err(Error::VmmThread)?;
 
-    Ok(api_socket_path)
+    r.map(|_| api_socket_path)
 }
 
 fn main() {