Eliminate type error on search_s

Guard the list comprehension to eliminate 'None' valued keys from
the attrlist from causing an exception when trying to iterate on
the None singleton.

related-bug: #1231772
Change-Id: I823a53d100b5e4210c767507e3233b61ed372068
Fix live LDAP tests

The live LDAP tests were failing. The tests for case
sensitivity for project name and user name failed because the
attribute is not case sensitive. The test for updating a
missing attribute with a falsy value was failing because the
attribute chosen for the project description does not allow an
empty string.

Change-Id: I723c40b5eab24ac13e27fd040d0d881998f106db
Related-Bug: #1231772
Merge "Eliminate type error on search_s"
Merge "Fix live LDAP tests"