bridge, del: timeout after 30 secs of trying to list rules

Making sure the exec'ed nft command is executed in 30 secs allows for
CNI to fail early, thus preventing CRI from sending another CNI DEL
while the previous NFT call is still being processed.

This fix prevents part of the behavior described in [0], in which:
> cnv-bridge and nft comes pile up in a loop, increasing every 60, never
completes

Signed-off-by: Miguel Duarte Barroso <mdbarroso@redhat.com>

pkg/link/spoofcheck.go

@@ -15,8 +15,10 @@
 package link
 
 import (
+	"context"
 	"fmt"
 	"os"
+	"time"
 
 	"github.com/networkplumbing/go-nft/nft"
 	"github.com/networkplumbing/go-nft/nft/schema"
@@ -46,7 +48,9 @@ func (dnc defaultNftConfigurer) Apply(cfg *nft.Config) error {
 }
 
 func (dnc defaultNftConfigurer) Read(filterCommands ...string) (*nft.Config, error) {
-	return nft.ReadConfig(filterCommands...)
+	ctxWithTimeout, cancelFunc := context.WithTimeout(context.Background(), time.Second)
+	defer cancelFunc()
+	return nft.ReadConfigContext(ctxWithTimeout, filterCommands...)
 }
 
 func NewSpoofChecker(iface, macAddress, refID string) *SpoofChecker {