afterEvaluate runs when project is already evaluated

[x] All tests passed. If this feature is not already covered by the tests, I added new tests.

Fix the following issue:

An exception occurred applying plugin request [id: 'com.jfrog.artifactory']
> Failed to apply plugin class 'org.jfrog.gradle.plugin.artifactory.ArtifactoryPlugin'.
   > Cannot run Project.afterEvaluate(Action) when the project is already evaluated.

The problem occurs when the plugin is used but not applied in the root project:

 id 'com.jfrog.artifactory' version '5.1.6' apply false

jfrog / artifactory-gradle-plugin

afterEvaluate runs when project is already evaluated #70