osbuild-run: remove any /etc/nsswitch.conf

On some hosts, systemd-tmpfiles will generate an nsswitch.conf
configuring DNS to be done via systemd-resolved, but this will
require the container to be booted and resolved to be running.

In other cases, a proper fall-back is configured, so this is not
a problem, but on some hosts this means DNS does not work.

Conversely, the default behavior with no nsswitch.conf at all
works just fine, always using nss-dns.

Let's simply delete the file if it is there, and rely on the
default.

Signed-off-by: Tom Gundersen <teg@jklm.no>

osbuild-run

@@ -60,12 +60,23 @@ def tmpfiles():
     subprocess.run(["systemd-tmpfiles", "--create"])
 
 
+def nsswitch():
+    # the default behavior is fine, but using nss-resolve does not
+    # necessarily work in a non-booted container, so make sure that
+    # is not configured.
+    try:
+        os.remove("/etc/nsswitch.conf")
+    except FileNotFoundError:
+        pass
+
+
 if __name__ == "__main__":
     ldconfig()
     sysusers()
     update_ca_trust()
     update_ca_certificates()
     tmpfiles()
+    nsswitch()
 
     r = subprocess.run(sys.argv[1:])
     sys.exit(r.returncode)