Fix errors when SOAP extension is not loaded

Initialize defaultSoapClientOptions property in setUp(), to avoid a
syntax error due to undefined constant WSDL_CACHE_NONE.

Remove useless SoapAllTests::setUp() method. TestSuite class does not
have this method so it is never actually called. Extension availability
check is performed by @requires extension hints in the test cases'
PHPDoc blocks.

Fixes 0032814