test: Add C unit test timeout
test: Add C unit test timeout

Similar to commit 90db3d2da7, prevent eternal hangs of the C unit tests.
This has commonly caused long-hanging semaphore or koji/brew builds.

Closes #14099

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