Fix qjson test of solidus encoding

"\/" is supposed to be decoded as "/", but there is no need to encode
"/" via escape. Fix the existing test and add a second one expressing
this.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Acked-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>

check-qjson.c

@@ -33,7 +33,8 @@ START_TEST(escaped_string)
         { "\"\\n\"", "\n" },
         { "\"\\r\"", "\r" },
         { "\"\\t\"", "\t" },
-        { "\"\\/\"", "\\/" },
+        { "\"/\"", "/" },
+        { "\"\\/\"", "/", .skip = 1 },
         { "\"\\\\\"", "\\" },
         { "\"\\\"\"", "\"" },
         { "\"hello world \\\"embedded string\\\"\"",