bridge: Handle ENOBUFS in packet channel
bridge: Handle ENOBUFS in packet channel

On some architectures at least, send(2) can fail with `ENOBUFS` on
congestion. Accept that as a transient error condition as well.

Also fix the broken check for EAGAIN/EINTR.

Closes  #12415
Fixes #12414
deryni/cockpit,cockpituous/cockpit,cockpit-project/cockpit,deryni/cockpit,cockpituous/cockpit,cockpit-project/cockpit,cockpit-project/cockpit,cockpituous/cockpit,moraleslazaro/cockpit,deryni/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,deryni/cockpit,martinpitt/cockpit,cockpituous/cockpit,martinpitt/cockpit,cockpituous/cockpit,mvollmer/cockpit,deryni/cockpit,garrett/cockpit,garrett/cockpit,martinpitt/cockpit,garrett/cockpit,cockpituous/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,cockpit-project/cockpit,martinpitt/cockpit,mvollmer/cockpit,deryni/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,garrett/cockpit,garrett/cockpit,martinpitt/cockpit,cockpit-project/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,deryni/cockpit