Update test RSA cert

[jbouwman]

Tests fail due to weak MD on self-signed RSA cert: update from SHA-1 to SHA-2.

New certificate is:

$ openssl x509 -in cert.pem -text -noout
Certificate:
    Data:
        Version: 3 (0x2)
        Serial Number:
            61:80:bc:12:c8:54:b0:15:1e:53:a2:06:d8:5c:ab:d4:da:fb:28:6d
        Signature Algorithm: sha256WithRSAEncryption
        Issuer: C = US, ST = Utah, L = Midvale, O = Space Monkey
        Validity
            Not Before: Aug 14 18:23:41 2021 GMT
            Not After : Jun 23 18:23:41 2031 GMT
        Subject: C = US, ST = Utah, L = Midvale, O = Space Monkey
        Subject Public Key Info:
            Public Key Algorithm: rsaEncryption
                RSA Public-Key: (2048 bit)
                Modulus:
                    00:dd:7f:78:9c:36:f1:6c:ae:5a:e7:34:b8:bc:4a:
                    87:2c:72:a9:52:6c:5a:be:a4:4b:e6:85:c4:a8:aa:
                    00:cb:a9:e6:e7:aa:ef:0b:77:bd:c7:24:9e:f8:30:
                    65:c4:81:15:fc:c5:94:f9:16:29:ce:30:bd:f5:09:
                    1e:ad:f4:4f:e3:dd:da:95:ea:9f:86:7d:d9:45:2d:
                    ed:c8:aa:d0:b4:fd:b3:d5:9c:20:c1:8a:b0:72:80:
                    12:38:b8:2a:cc:ab:ed:55:84:0c:4f:59:c9:6b:0e:
                    8e:e5:f5:04:58:6e:c1:31:1f:d9:5f:9f:e4:72:bf:
                    17:8d:31:98:8e:01:26:ac:bd:56:4d:9d:c6:3c:13:
                    db:ac:04:64:5d:1f:5e:c4:7c:32:ff:4c:fc:17:a9:
                    63:8b:cb:14:8d:e6:8e:78:19:3c:ed:8e:3c:bd:c3:
                    d0:86:40:fe:e3:70:2b:9e:29:8c:90:25:00:ad:12:
                    69:f0:73:a3:ff:ab:af:c4:3e:fe:51:e9:da:c1:91:
                    7e:a5:a0:03:ed:98:25:00:90:7a:b1:91:63:89:ad:
                    1a:bf:bf:b3:f0:cd:16:21:7d:8f:99:a5:51:c6:73:
                    b5:84:90:39:cb:cd:18:94:ca:9a:f5:0b:da:31:bc:
                    b2:92:d7:47:ad:64:42:30:11:d2:b2:3a:44:a0:d9:
                    f7:4f
                Exponent: 65537 (0x10001)
        X509v3 extensions:
            X509v3 Subject Key Identifier: 
                A3:F1:9E:9D:D9:3A:9A:71:13:F8:6A:59:70:40:CD:45:62:09:6D:3F
            X509v3 Authority Key Identifier: 
                keyid:A3:F1:9E:9D:D9:3A:9A:71:13:F8:6A:59:70:40:CD:45:62:09:6D:3F

            X509v3 Basic Constraints: critical
                CA:TRUE
    Signature Algorithm: sha256WithRSAEncryption
         36:28:92:e8:15:6a:2b:67:3f:ad:6f:f1:dd:0c:94:d3:0f:1c:
         b9:fd:78:4e:9f:1f:b6:38:80:0b:16:c2:c9:9e:e9:68:f1:f1:
         db:26:73:ca:b2:97:b6:57:4f:04:70:56:74:85:4a:ef:2a:c6:
         97:a6:6f:15:5d:7d:b5:c8:e1:60:e7:23:1c:ac:6e:80:de:fa:
         10:58:88:ef:4c:23:70:7f:2c:27:a6:7b:31:ad:6c:21:b9:1a:
         a2:a1:49:91:e1:64:96:36:81:6e:c2:0f:a5:b7:a6:cb:0d:ab:
         cc:e0:8c:e5:f3:a3:5b:fc:ba:00:cc:a7:3a:83:a9:ca:18:72:
         89:2e:e2:66:6b:a4:4f:26:79:a3:7c:2e:0e:b3:51:96:7f:ba:
         df:91:03:8f:fd:77:40:d2:df:89:5b:5f:80:04:17:4e:77:99:
         0e:b6:8c:00:bd:02:ca:cc:b6:22:eb:14:eb:bc:40:d2:8c:3b:
         62:29:2e:36:75:5c:9d:06:98:f7:51:a8:a1:b4:2c:dc:89:e4:
         1b:6f:a2:aa:53:2c:71:ce:04:de:95:7a:b6:23:12:54:c9:4e:
         f8:26:ff:7a:05:9f:1c:03:b4:2f:c2:fd:63:c2:c7:f1:62:fe:
         d5:1c:bb:85:02:6b:56:28:20:c5:98:b8:cc:b5:da:ca:5f:ea:
         b9:cc:97:bb

[BigLep]

@marten-seemann : can you take getting this merged and getting CI running. @Stebalien has some prior art apparently.

[marten-seemann]

Thank you!