lib/{curl,upnp}: add more exception handlers

Bugs found by Coverity.

src/lib/curl/Request.cxx

@@ -72,7 +72,7 @@ CurlRequest::~CurlRequest() noexcept
 }
 
 void
-CurlRequest::Start() noexcept
+CurlRequest::Start()
 {
 	assert(!registered);