channel_wait_closed: don't fail when unread data is queued
channel_wait_closed: don't fail when unread data is queued

This function was calling channel_wait_eof to ensure that the EOF
packet has already been received, but that function also checks that
the read data queue is empty before reporting the EOF. That caused
channel_wait_closed to fail with a LIBSSH2_ERROR_INVAL when some data
was queued even after a successful call to libssh2_channel_wait_eof.

This patch changes libssh2_channel_wait_closed to look directly into
channel->remote.eof so that both libssh2_channel_wait_eof and
libssh2_channel_wait_closed bahave consistently.

libssh2/libssh2,libssh2/libssh2,libssh2/libssh2,libssh2/libssh2