Remove bandwidth attributes when disabling a stream

Ignore-this: d13fe160710e0b55bd51ff3586b00399

darcs-hash:20141117161344-56b4d-142f7b4df261e44c3def1761b9b8f8769531840a
Fixed missing return statement

Ignore-this: 56f5d527ea8e626b3db1e0edb984a064

darcs-hash:20141117163201-56b4d-a2632603ab3c6983079fad3e6c9ebbdd097a4cfc
Reject incoming re-INVITE if we couldn't reply to it

Ignore-this: a160cb766e08c47ad4055dd340521313

Only do it if it wasn't a stream removal, that is, if the remote party
tried to change some session / stream parameters for which we couldn't
build an answer. This is a best effort approach.

darcs-hash:20141117175048-56b4d-99cf842168eb2a471707c2c87781e544c03833a0
Simplified code

Ignore-this: 38d8955550593ba550c4e699dc410b89

darcs-hash:20141118102309-56b4d-f04b790a3f0fc249b62c9bdc72bac499fb1ad85b