Removing TextString check to encode characters when writing bytes

This change removes extraneous code in the TextString primitive
that would conditionally encode the individual string characters
depending upon the version of Python being used. This code caused
errors when using Unicode strings in Python 2.7 and below.

kmip/core/primitives.py

@@ -810,11 +810,7 @@ class TextString(Base):
     def write_value(self, ostream):
         # Write string to stream
         for char in self.value:
-            if sys.version < '3':
-                c = char
-            else:
-                c = char.encode()
-            ostream.write(pack(self.BYTE_FORMAT, c))
+            ostream.write(pack(self.BYTE_FORMAT, char.encode()))
 
         # Write padding to stream
         for _ in range(self.padding_length):