Block asyncs when starting inferiors

Because this code deals with global state, like environment variables.

guix-data-service/jobs/load-new-guix-revision.scm

@@ -1330,6 +1330,8 @@
 
 (define (start-inferior-for-data-extration store store-path guix-locpath
                                            extra-inferior-environment-variables)
+  (call-with-blocked-asyncs
+   (lambda ()
      (let* ((original-guix-locpath (getenv "GUIX_LOCPATH"))
             (original-extra-env-vars-values
              (map (match-lambda
@@ -1418,7 +1420,7 @@
        ((@@ (guix inferior) ensure-store-bridge!) inf)
        (non-blocking-port ((@@ (guix inferior) inferior-bridge-socket) inf))
 
-    inf))
+       inf))))
 
 (define* (extract-information-from conn long-running-store-connection
                                    guix-revision-id commit