tests: print enum type members more like object type members

Commit 93bda4dd46 changed the internal representation of enum type
members from str to QAPISchemaMember, but we still print only a
string.  Has been good enough, as the name is the member's only
attribute of interest, but that's about to change.  To prepare, print
them more like object type members.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20181213123724.4866-4-marcandre.lureau@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

tests/qapi-schema/doc-good.out

@@ -1,8 +1,17 @@
 object q_empty
-enum QType ['none', 'qnull', 'qnum', 'qstring', 'qdict', 'qlist', 'qbool']
+enum QType
     prefix QTYPE
+    member none
+    member qnull
+    member qnum
+    member qstring
+    member qdict
+    member qlist
+    member qbool
 module doc-good.json
-enum Enum ['one', 'two']
+enum Enum
+    member one
+    member two
     if ['defined(IFCOND)']
 object Base
     member base1: Enum optional=False
@@ -18,7 +27,9 @@ object q_obj_Variant1-wrapper
     member data: Variant1 optional=False
 object q_obj_Variant2-wrapper
     member data: Variant2 optional=False
-enum SugaredUnionKind ['one', 'two']
+enum SugaredUnionKind
+    member one
+    member two
 object SugaredUnion
     member type: SugaredUnionKind optional=False
     tag type