Fix location of vk_layer_settings.txt on Android

Commit 969ab0680dd434f0 ('api_dump: Support config file and logging on Android')
added a custom location for vk_layer_settings.txt on Android. However, commit
750837a5dedf524c81c (Merge branch 'trunk') ended up partly overwriting these changes,
breaking the functionality.

As a result, using the config file on Android hasn't worked since October 2016. This commit
restores the changes in the original commit to fix this.
diff --git a/layers/vk_layer_config.cpp b/layers/vk_layer_config.cpp
index ffefbcd..1f32eff 100644
--- a/layers/vk_layer_config.cpp
+++ b/layers/vk_layer_config.cpp
@@ -192,7 +192,7 @@
             }
             parseFile(envPath.c_str());
         } else {
-            parseFile("vk_layer_settings.txt");
+            parseFile(m_fileName.c_str());
         }
     }
 
@@ -215,7 +215,7 @@
             }
             parseFile(envPath.c_str());
         } else {
-            parseFile("vk_layer_settings.txt");
+            parseFile(m_fileName.c_str());
         }
     }