[Fix] Fix wandb logger drop result bug (#913)

* fix wandb logger drop result bug by delete step param

* add global_step in wandb log to help align train and val step log

* fix wandb hook test unit fail bug

* fix lint issue

* add with_step param of WandbLoggerHook in wandb.py

mmcv/runner/hooks/logger/wandb.py

@@ -13,12 +13,14 @@ def __init__(self,
                  ignore_last=True,
                  reset_flag=True,
                  commit=True,
-                 by_epoch=True):
+                 by_epoch=True,
+                 with_step=True):
         super(WandbLoggerHook, self).__init__(interval, ignore_last,
                                               reset_flag, by_epoch)
         self.import_wandb()
         self.init_kwargs = init_kwargs
         self.commit = commit
+        self.with_step = with_step
 
     def import_wandb(self):
         try:
@@ -41,8 +43,12 @@ def before_run(self, runner):
     def log(self, runner):
         tags = self.get_loggable_tags(runner)
         if tags:
-            self.wandb.log(
-                tags, step=self.get_iter(runner), commit=self.commit)
+            if self.with_step:
+                self.wandb.log(
+                    tags, step=self.get_iter(runner), commit=self.commit)
+            else:
+                tags['global_step'] = self.get_iter(runner)
+                self.wandb.log(tags, commit=self.commit)
 
     @master_only
     def after_run(self, runner):