Allow dlopening public libs using absolute path

dlopen on isolated namespaces should be able to open
public libraries using absolute path not only soname.

Bug: http://b/25853820
Change-Id: If574a67853dc51226f0f376e9e2d108316002f84

linker/linker.cpp

@@ -1582,9 +1582,6 @@ static int open_library(android_namespace_t* ns,
       }
     }
 
-    if (fd != -1 && !ns->is_accessible(*realpath)) {
-      fd = -1;
-    }
     return fd;
   }
 
@@ -1701,6 +1698,13 @@ static bool load_library(android_namespace_t* ns,
     return false;
   }
 
+  if (!ns->is_accessible(realpath)) {
+    // do not load libraries if they are not accessible for the specified namespace.
+    DL_ERR("library \"%s\" is not accessible for the namespace \"%s\"",
+           name, ns->get_name());
+    return false;
+  }
+
   soinfo* si = soinfo_alloc(ns, realpath.c_str(), &file_stat, file_offset, rtld_flags);
   if (si == nullptr) {
     return false;