rpc: fix race on stream abort/finish and server side abort

rpc: fix race on stream abort/finish and server side abort

Stream abort/finish can hang because we can receive abort message
from server and yet sent abort/finish message to server. The latter
will not be answered ever because after server sends abort message
it forgets the stream and messages for unknown stream are simply ignored.

We check for stream error at the very beginning of remoteStreamFinish/remoteStreamAbort
but stream error can be set after the check in another thread operating
on stream. Let's check for stream error under client lock similar
to what's done in [1].

[1] 833b901cb: stream: Check for stream EOF

Signed-off-by: Nikolay Shirokovskiy <nshirokovskiy@virtuozzo.com>