Refactor postgresql modules (#291)

* Refactor postgresql_idx to simplify code

Have refactored the postgresql_idx module to:
* Use the class schema in the drop function rather than a passed in one
* Remove the if/else and just return the bool in the drop and create
  functions

* Refactor postgresql_ext module

Have refactored the postgresql_ext module to:
* Remove an unused exception
* Simplify logic in the create and update functions
* Use list comprehension to simplify getting the available version

* Refactor postgresql_user_obj_stat_info module

Have refactored the postgresql_user_obj_stat_info module to:
* Simplify the logic in some of the functions
* Reduce duplicate code

* Add changelog fragment

plugins/modules/database/postgresql/postgresql_idx.py

@@ -145,6 +145,7 @@ notes:
 
 author:
 - Andrew Klychkov (@Andersson007)
+- Thomas O'Donnell (@andytom)
 
 extends_documentation_fragment:
 - community.general.postgres
@@ -418,12 +419,9 @@ class Index(object):
 
         self.executed_query = query
 
-        if exec_sql(self, query, return_bool=True, add_to_executed=False):
-            return True
+        return exec_sql(self, query, return_bool=True, add_to_executed=False)
 
-        return False
-
-    def drop(self, schema, cascade=False, concurrent=True):
+    def drop(self, cascade=False, concurrent=True):
         """Drop PostgreSQL index.
 
         Return True if success, otherwise, return False.
@@ -444,20 +442,14 @@ class Index(object):
         if concurrent:
             query += ' CONCURRENTLY'
 
-        if not schema:
-            query += ' "public"."%s"' % self.name
-        else:
-            query += ' "%s"."%s"' % (schema, self.name)
+        query += ' "%s"."%s"' % (self.schema, self.name)
 
         if cascade:
             query += ' CASCADE'
 
         self.executed_query = query
 
-        if exec_sql(self, query, return_bool=True, add_to_executed=False):
-            return True
-
-        return False
+        return exec_sql(self, query, return_bool=True, add_to_executed=False)
 
 
 # ===========================================
@@ -579,7 +571,7 @@ def main():
             kw['query'] = index.executed_query
 
     else:
-        changed = index.drop(schema, cascade, concurrent)
+        changed = index.drop(cascade, concurrent)
 
         if changed:
             kw['state'] = 'absent'