bridge: Make PTY resizing test resistant to kernel bug
bridge: Make PTY resizing test resistant to kernel bug

Sometimes `TIOCSWINSZ` just gets silently ignored. `SIGWINCH` is being
delivered to the child, but the actual PTY size never changes. This is
exposed by occasional failures of the /pipe-channel/spawn/pty-resize
unit test.

As there is no known fix for now, and also no work around on the parent
size (see PR history), retry PTY ressize up to five times before giving
up.

See https://bugzilla.redhat.com/show_bug.cgi?id=1693179
Related issue #11454

Closes #11476

mvollmer/cockpit,mvollmer/cockpit,cockpituous/cockpit,garrett/cockpit,martinpitt/cockpit,garrett/cockpit,deryni/cockpit,cockpituous/cockpit,martinpitt/cockpit,deryni/cockpit,deryni/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,deryni/cockpit,cockpit-project/cockpit,cockpituous/cockpit,deryni/cockpit,martinpitt/cockpit,martinpitt/cockpit,deryni/cockpit,martinpitt/cockpit,garrett/cockpit,cockpituous/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,garrett/cockpit,cockpit-project/cockpit,moraleslazaro/cockpit,garrett/cockpit,moraleslazaro/cockpit,cockpit-project/cockpit,cockpituous/cockpit,cockpit-project/cockpit,cockpituous/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,moraleslazaro/cockpit,moraleslazaro/cockpit,mvollmer/cockpit,deryni/cockpit