wic: remove PluginMgr.get_source_plugins

Used get_plugins('source') instead of get_source_plugins to
unify and simplify API to get plugins.

(From OE-Core rev: aaab003e472416124d7342fc8c4a17c252b83f4d)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/wic/engine.py

@@ -139,7 +139,7 @@ def list_source_plugins():
     """
     List the available source plugins i.e. plugins available for --source.
     """
-    plugins = PluginMgr.get_source_plugins()
+    plugins = PluginMgr.get_plugins('source')
 
     for plugin in plugins:
         print("  %s" % plugin)

scripts/lib/wic/partition.py

@@ -154,7 +154,7 @@ class Partition():
                         break
             return
 
-        plugins = PluginMgr.get_source_plugins()
+        plugins = PluginMgr.get_plugins('source')
 
         if self.source not in plugins:
             raise WicError("The '%s' --source specified for %s doesn't exist.\n\t"

scripts/lib/wic/plugin.py

@@ -108,18 +108,6 @@ class PluginMgr:
 
         return pluginbase.get_plugins(ptype)
 
-    @classmethod
-    def get_source_plugins(cls):
-        """
-        Return list of available source plugins.
-        """
-        plugins_dir = cls._build_plugin_dir_list(cls.plugin_dir, 'source')
-
-        cls.append_dirs(plugins_dir)
-
-        return cls.get_plugins('source')
-
-
     @classmethod
     def get_source_plugin_methods(cls, source_name, methods):
         """