DebugInfo: Remove some unneeded conditionals now that DIBuilder no longer emits zero-length arrays as {i32 0}

A bunch of test cases needed to be cleaned up for this, many my fault -
when implementid imported modules I updated test cases by simply
duplicating the prior metadata field - which wasn't always the empty
metadata entry.

llvm-svn: 200731
diff --git a/llvm/test/DebugInfo/X86/gnu-public-names.ll b/llvm/test/DebugInfo/X86/gnu-public-names.ll
index 856973a..b899782 100644
--- a/llvm/test/DebugInfo/X86/gnu-public-names.ll
+++ b/llvm/test/DebugInfo/X86/gnu-public-names.ll
@@ -256,7 +256,7 @@
 
 !0 = metadata !{i32 786449, metadata !1, i32 4, metadata !"clang version 3.4 (trunk 192862) (llvm/trunk 192861)", i1 false, metadata !"", i32 0, metadata !2, metadata !3, metadata !21, metadata !29, metadata !2, metadata !""} ; [ DW_TAG_compile_unit ] [/usr/local/google/home/echristo/tmp/pubnames.cpp] [DW_LANG_C_plus_plus]
 !1 = metadata !{metadata !"pubnames.cpp", metadata !"/usr/local/google/home/echristo/tmp"}
-!2 = metadata !{i32 0}
+!2 = metadata !{}
 !3 = metadata !{metadata !4, metadata !17}
 !4 = metadata !{i32 786451, metadata !1, null, metadata !"C", i32 1, i64 8, i64 8, i32 0, i32 0, null, metadata !5, i32 0, null, null, metadata !"_ZTS1C"} ; [ DW_TAG_structure_type ] [C] [line 1, size 8, align 8, offset 0] [def] [from ]
 !5 = metadata !{metadata !6, metadata !8, metadata !13}