fix: allowMocked when using a callback for the path

When an Interceptor was created with a comparator for the path, the
`matchOrigin` function was comparing the string equivalent of the function
instead of evaluating it.

I'm not a fan of the fact that the function `matchOrigin` is comparing the
pathname, but that's a refactor for another day.

Fixes: nock#1867

lib/interceptor.js

@@ -355,6 +355,7 @@ module.exports = class Interceptor {
    * match the provided options.
    */
   matchOrigin(options) {
+    const isPathFn = typeof this.path === 'function';
     const isRegex = this.path instanceof RegExp
     const isRegexBasePath = this.scope.basePath instanceof RegExp
 
@@ -370,9 +371,13 @@ module.exports = class Interceptor {
     if (this.scope.transformPathFunction) {
       path = this.scope.transformPathFunction(path)
     }
-    const comparisonKey = isRegex ? this.__nock_scopeKey : this._key
+    const comparisonKey = isPathFn || isRegex ? this.__nock_scopeKey : this._key
     const matchKey = `${method} ${proto}://${options.host}${path}`
 
+    if(isPathFn) {
+      return !!(matchKey.match(comparisonKey) && this.path(path))
+    }
+
     if (isRegex && !isRegexBasePath) {
       return !!matchKey.match(comparisonKey) && this.path.test(path)
     }