ovs-monitor-ipsec: Fix _nss_clear_database() parse error.

_nss_clear_database() runs `certutil` in order to get a list
of certificates currently loaded in NSS. This fails with error:

"ovs-monitor-ipsec | ERR | Failed to clear NSS database.
startswith first arg must be bytes or a tuple of bytes, not str"

Modify subprocess.Popen() to write in 'text' mode so that
'startwith' can correctly parse output.

Signed-off-by: Mark Gray <mark.d.gray@redhat.com>
Acked-by: Eelco Chaudron <echaudro@redhat.com>
Acked-by: Flavio Leitner <fbl@sysclose.org>
Signed-off-by: Ilya Maximets <i.maximets@ovn.org>

ipsec/ovs-monitor-ipsec.in

@@ -657,7 +657,8 @@ conn prevent_unencrypted_vxlan
             proc = subprocess.Popen(['certutil', '-L', '-d',
                                     'sql:/etc/ipsec.d/'],
                                     stdout=subprocess.PIPE,
-                                    stderr=subprocess.PIPE)
+                                    stderr=subprocess.PIPE,
+                                    universal_newlines=True)
             lines = proc.stdout.readlines()
 
             for line in lines: