Fixes the qtIdent function in the psycopg2 driver about not taking care

of double quote within it.

The 'replace' function of immutable type string do create a new
instance of type string, which needed to be reassgined to the variable
'value'.

Reported By: Murtuza Zabuawala

web/pgadmin/utils/driver/psycopg2/__init__.py

@@ -894,7 +894,7 @@ class Driver(BaseDriver):
             value = val
 
             if (Driver.needsQuoting(val, True)):
-                value.replace("\"", "\"\"")
+                value = value.replace("\"", "\"\"")
                 value = "\"" + value + "\""
 
             res = ((res and res + '.') or '') + value
@@ -918,7 +918,7 @@ class Driver(BaseDriver):
             value = val
 
             if (Driver.needsQuoting(val, False)):
-                value.replace("\"", "\"\"")
+                value = value.replace("\"", "\"\"")
                 value = "\"" + value + "\""
 
             res = ((res and res + '.') or '') + value