UA.configuration_check.optional.mediaHandlerFactory preserves isSupported property
UA.configuration_check.optional.mediaHandlerFactory preserves isSupported property

pass test added in previous commit

see f3e5cfa40bb99df33bfc830987263b36794db9d8

joseph-onsip/SIP.js,onsip/SIP.js,onsip/SIP.js,ronlobo/SIP.js,Escaux/SIP.js,markandrus/SIP.js,josephfrazier/SIP.js