Improve error message for conflicting HAL major versions.

Provide more debug information (specifically, names of files where
the conflicting entry is located).

Test: libvintf_test
Test: vintf_object_test
Test: manually create a conflict, then m check-vintf-all
Fixes: 118757553

Change-Id: I45b2262936975df947fbd0864477f32e18ce813a
diff --git a/VintfObject.cpp b/VintfObject.cpp
index 090f582..f70c4f8 100644
--- a/VintfObject.cpp
+++ b/VintfObject.cpp
@@ -221,7 +221,7 @@
 
         if (!manifest->addAll(&fragmentManifest, error)) {
             if (error) {
-                error->insert(0, "Cannot add manifest fragment " + directory + file + ":");
+                error->insert(0, "Cannot add manifest fragment " + directory + file + ": ");
             }
             return UNKNOWN_ERROR;
         }