Remove ucloud_common and put its files under ucloud.common subpackage.

Remove individual config.py used by every component and put them into single config.py ucloud/config.py
Use /etc/ucloud/ucloud.conf for Environment Variables
Refactoring and a lot of it
Make ucloud repo a package and different components of ucloud a subpackage for avoiding code duplication.
Improved logging.

ucloud.py

@@ -1,16 +1,50 @@
 import argparse
-import subprocess as sp
-arg_parser = argparse.ArgumentParser(prog='ucloud',
-                                     description='Open Source Cloud Management Software')
-arg_parser.add_argument('component',
-                        choices=['api', 'scheduler', 'host',
-                                 'filescanner','imagescanner',
-                                 'metadata'])
-arg_parser.add_argument('component_args', nargs='*')
-args = arg_parser.parse_args()
+import multiprocessing as mp
+import logging
 
-try:
-    command = ['pipenv', 'run', 'python', 'main.py', *args.component_args]
-    sp.run(command, cwd=args.component)
-except Exception as error:
-    print(error)
+from os.path import join as join_path
+
+if __name__ == "__main__":
+    arg_parser = argparse.ArgumentParser(prog='ucloud',
+                                         description='Open Source Cloud Management Software')
+    arg_parser.add_argument('component',
+                            choices=['api', 'scheduler', 'host',
+                                     'filescanner', 'imagescanner',
+                                     'metadata'])
+    arg_parser.add_argument('component_args', nargs='*')
+    args = arg_parser.parse_args()
+
+    logging.basicConfig(
+        level=logging.DEBUG,
+        filename=join_path("logs.txt"),
+        filemode="a",
+        format="%(name)s %(asctime)s: %(levelname)s - %(message)s",
+        datefmt="%d-%b-%y %H:%M:%S",
+    )
+
+    if args.component == 'api':
+        from api.main import main
+
+        main()
+    elif args.component == 'host':
+        from host.main import main
+
+        hostname = args.component_args
+        mp.set_start_method('spawn')
+        main(*hostname)
+    elif args.component == 'scheduler':
+        from scheduler.main import main
+
+        main()
+    elif args.component == 'filescanner':
+        from filescanner.main import main
+
+        main()
+    elif args.component == 'imagescanner':
+        from imagescanner.main import main
+
+        main()
+    elif args.component == 'metadata':
+        from metadata.main import main
+
+        main()