Fix alias tests to use default-branches

tests/Composer/Test/DependencyResolver/Fixtures/poolbuilder/alias-priority-conflicting.test

@@ -35,16 +35,19 @@ Check root aliases are loaded
     {
         "name": "req/pkg", "version": "dev-master",
         "extra": { "branch-alias": { "dev-master": "1.0.x-dev" } },
-        "source": { "reference": "forked", "type": "git", "url": "" }
+        "source": { "reference": "forked", "type": "git", "url": "" },
+        "default-branch": true
     },
     {
         "name": "req/pkg", "version": "dev-master",
         "extra": { "branch-alias": { "dev-master": "1.0.x-dev" } },
-        "source": { "reference": "master", "type": "git", "url": "" }
+        "source": { "reference": "master", "type": "git", "url": "" },
+        "default-branch": true
     },
     {
         "name": "package/a", "version": "dev-master",
-        "require": { "req/pkg": "dev-master" }
+        "require": { "req/pkg": "dev-master" },
+        "default-branch": true
     }
 ]
 

tests/Composer/Test/DependencyResolver/Fixtures/poolbuilder/alias-with-reference.test

@@ -35,7 +35,8 @@ Check root aliases get selected correctly
 [
     {
         "name": "a/aliased", "version": "dev-master",
-        "source": { "reference": "orig", "type": "git", "url": "" }
+        "source": { "reference": "orig", "type": "git", "url": "" },
+        "default-branch": true
     },
     {
         "name": "a/aliased", "version": "1.0"