improve install script & site.py

* remove php7.2 installation
* cleanup code
* improve code quality according to shellcheck warnings

wo/cli/plugins/clean.py

@@ -53,6 +53,7 @@ class WOCleanController(CementBaseController):
             self.clean_opcache()
         if self.app.pargs.redis:
             self.clean_redis()
+
     @expose(hide=True)
     def clean_redis(self):
         """This function clears Redis cache"""
@@ -97,6 +98,7 @@ class WOCleanController(CementBaseController):
                          " or install them with `wo stack install --admin`")
                 Log.error(self, "Unable to clean opcache", False)
 
+
 def load(app):
     # register the plugin class.. this only happens if the plugin is enabled
     handler.register(WOCleanController)