Replace PhotoDB.normalize_tagname with real call to Tag.norm_name.

I originally did this because I didn't want to accidentally call
Tag.normalize_name and forget to pass the valid parameters. However,
having this single method be on PhotoDB while the other norms are
part of their proper class has been an eyesore.
So since there are only a few calls to this I'm just inlining them
and trusting to not forget if I add more in the future.

etiquette/photodb.py

@@ -828,7 +828,12 @@ class PDBTagMixin:
             tagname = tagname.tagname
 
         try:
-            tagname = self.normalize_tagname(tagname)
+            tagname = objects.Tag.normalize_name(
+                tagname,
+                valid_chars=self.config['tag']['valid_chars'],
+                min_length=self.config['tag']['min_length'],
+                max_length=self.config['tag']['max_length'],
+            )
         except (exceptions.TagTooShort, exceptions.TagTooLong):
             raise exceptions.NoSuchTag(tagname)
 
@@ -865,7 +870,12 @@ class PDBTagMixin:
         '''
         Register a new tag and return the Tag object.
         '''
-        tagname = self.normalize_tagname(tagname)
+        tagname = objects.Tag.normalize_name(
+            tagname,
+            valid_chars=self.config['tag']['valid_chars'],
+            min_length=self.config['tag']['min_length'],
+            max_length=self.config['tag']['max_length'],
+        )
         self.assert_no_such_tag(name=tagname)
 
         description = objects.Tag.normalize_description(description)
@@ -888,15 +898,6 @@ class PDBTagMixin:
         tag = self.get_cached_instance('tag', data)
         return tag
 
-    def normalize_tagname(self, tagname):
-        tagname = objects.Tag.normalize_name(
-            tagname,
-            valid_chars=self.config['tag']['valid_chars'],
-            min_length=self.config['tag']['min_length'],
-            max_length=self.config['tag']['max_length'],
-        )
-        return tagname
-
 
 class PDBUserMixin:
     def __init__(self):