install: Fix complete brokenness

Argh. No more 4am releases. Most (but not ALL) `npm install` use cases
were instant crashers. I apparently THEN went on to run the test suite
against the wrong tree. =( =(

PR-URL: #8922
Fixes #8893

lib/install.js

@@ -574,19 +574,20 @@ Installer.prototype.readLocalPackageData = function (cb) {
         return cb(er)
       }
       if (!currentTree.package) currentTree.package = {}
-      if (currentTree.package._shrinkwrap) return cb()
-      fs.readFile(path.join(self.where, 'npm-shrinkwrap.json'), function (er, data) {
-        if (er) return cb()
-        try {
-          currentTree.package._shrinkwrap = parseJSON(data)
-        } catch (ex) {
-          return cb(ex)
-        }
-        return this.loadArgMetadata(cb)
-      })
+      self.loadArgMetadata(iferr(cb, function () {
+        if (currentTree.package._shrinkwrap) return cb()
+        fs.readFile(path.join(self.where, 'npm-shrinkwrap.json'), function (er, data) {
+          if (er) return cb()
+          try {
+            currentTree.package._shrinkwrap = parseJSON(data)
+          } catch (ex) {
+            return cb(ex)
+          }
+          return cb()
+        })
+      }))
     }))
   }))
-
 }
 
 Installer.prototype.cloneCurrentTreeToIdealTree = function (cb) {