test-tool: add iSCSICHAP.Base64 test

Some targets such as LIO support base64 encoded CHAP_R values. Test this
by intercepting hex-encoded CHAP_R responses and converting the value to
base64.
This will fail on targets which don't support base64; we should probably
skip the test instead.
base64 encoding is performed using the gnutls_base64_encode2() function,
so the test is only present for gnutls-enabled builds.

Signed-off-by: David Disseldorp <ddiss@suse.de>

test-tool/iscsi-test-cu.h

@@ -87,6 +87,9 @@ void test_iscsi_sendtargets_invalid(void);
 void test_iscsi_nop_simple(void);
 void test_iscsi_chap_simple(void);
 void test_iscsi_chap_invalid(void);
+#ifdef HAVE_LIBGNUTLS
+void test_iscsi_chap_base64(void);
+#endif
 
 void test_mandatory_sbc(void);