cmd: don't alias context package, and use cliContext for cli.Context

Unfortunately, this is a rather large diff, but perhaps worth a one-time
"rip off the bandaid" for v2. This patch removes the use of "gocontext"
as alias for stdLib's "context", and uses "cliContext" for uses of
cli.context.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

cmd/ctr/commands/tasks/tasks.go

@@ -17,13 +17,13 @@
 package tasks
 
 import (
-	gocontext "context"
+	"context"
 
 	"github.com/urfave/cli/v2"
 )
 
 type resizer interface {
-	Resize(ctx gocontext.Context, w, h uint32) error
+	Resize(ctx context.Context, w, h uint32) error
 }
 
 // Command is the cli command for managing tasks