tests: fix key generation for dom0 updates tests

gpg2 requires explicit `%no-protection`, otherwise tries to
interactively (through gpg-agent) prompt for the passphrase.

qubes/tests/integ/dom0_update.py

@@ -54,6 +54,7 @@ Key-Length: 1024
 Key-Usage: sign
 Name-Real: Qubes test
 Expire-Date: 0
+%no-protection
 %commit
         '''.format(keydir=keydir).encode())
         p.stdin.close()