Rename --unique-id to --force-job-id

Also improve its documentation, explaining that users should
not use this option unless they know exactly what they're doing
Signed-off-by: NAdemar de Souza Reis Jr <areis@redhat.com>

avocado/job.py

@@ -283,7 +283,7 @@ class Job(object):
         """
         self.args = args
         if args is not None:
-            self.unique_id = args.unique_id or job_id.get_job_id()
+            self.unique_id = args.unique_job_id or job_id.get_job_id()
         else:
             self.unique_id = job_id.get_job_id()
         self.logdir = data_dir.get_job_logs_dir(self.args, self.unique_id)

avocado/plugins/runner.py

@@ -108,10 +108,12 @@ class TestRunner(plugin.Plugin):
         self.parser.add_argument('--keep-tmp-files', action='store_true', default=False,
                                  help='Keep temporary files generated by tests')
 
-        self.parser.add_argument('--unique-id', type=str, default=None,
-                                 help=('Unique Job id. Used by a server when job '
-                                       'was created at the server and run on a '
-                                       'different test machine'))
+        self.parser.add_argument('--force-job-id', dest='unique_job_id',
+                                 type=str, default=None,
+                                 help=('Forces the use of a particular job ID. Used '
+                                       'internally when interacting with an avocado '
+                                       'server. You should not use this option '
+                                       'unless you know exactly what you\'re doing'))
 
         self.parser.add_argument('-s', '--silent', action='store_true', default=False,
                                  help='Silent output, do not display results.')