Convert certificate tests to httpretty

Change-Id: Ic7eacb75f90b383ecacf01269033c0a37bd7528c
blueprint: httpretty-testing
Convert Cloud Pipe tests to httpretty

Change-Id: I0a737a5c66831edafbd671bfd49017bc1274fca3
blueprint: httpretty-testing
Convert Fixed IP tests to httpretty

Change-Id: I90a14b51dba6c0b64f0a264e762a0795a2566ae6
blueprint: httpretty-testing
Merge "Convert certificate tests to httpretty"
Merge "Convert Cloud Pipe tests to httpretty"
Merge "Convert Fixed IP tests to httpretty"