Add tests for spurious certs in the chain

We have code to skip them but didn't have explicit tests ensuring they are
(the corresponding branch was never taken).

While at it, remove extra copy of the chain in server10*.crt, which was
duplicated for no reason.
diff --git a/tests/suites/test_suite_x509parse.data b/tests/suites/test_suite_x509parse.data
index b0445e0..092b9e8 100644
--- a/tests/suites/test_suite_x509parse.data
+++ b/tests/suites/test_suite_x509parse.data
@@ -747,6 +747,14 @@
 depends_on:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECP_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_ECP_DP_SECP384R1_ENABLED:MBEDTLS_SHA1_C:MBEDTLS_SHA256_C
 x509_verify:"data_files/server5.crt":"data_files/test-ca2_cat-past-invalid.crt":"data_files/crl-ec-sha1.pem":"NULL":MBEDTLS_ERR_X509_CERT_VERIFY_FAILED:MBEDTLS_X509_BADCERT_EXPIRED:"compat":"NULL"
 
+X509 Certificate verification #88 (Spurious cert in the chain)
+depends_on:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_ECP_DP_SECP384R1_ENABLED:MBEDTLS_SHA1_C:MBEDTLS_SHA256_C:MBEDTLS_RSA_C
+x509_verify:"data_files/server7_spurious_int-ca.crt":"data_files/test-ca2.crt":"data_files/crl-ec-sha1.pem":"NULL":0:0:"compat":"NULL"
+
+X509 Certificate verification #89 (Spurious cert later in the chain)
+depends_on:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_ECP_DP_SECP384R1_ENABLED:MBEDTLS_SHA1_C:MBEDTLS_SHA256_C:MBEDTLS_RSA_C
+x509_verify:"data_files/server10_int3_spurious_int-ca2.crt":"data_files/test-ca.crt":"data_files/crl-ec-sha1.pem":"NULL":0:0:"compat":"NULL"
+
 X509 Certificate verification callback: trusted EE cert
 depends_on:MBEDTLS_PEM_PARSE_C:MBEDTLS_ECDSA_C:MBEDTLS_SHA256_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED
 x509_verify_callback:"data_files/server5-selfsigned.crt":"data_files/server5-selfsigned.crt":0:"depth 0 - serial 53\:A2\:CB\:4B\:12\:4E\:AD\:83\:7D\:A8\:94\:B2 - subject CN=selfsigned, OU=testing, O=PolarSSL, C=NL\n"