Rework the way database is open/re-open in aptly

Allow database to be initialized without opening, unify all the
open paths to retry on failure.

In API router make sure open requests are matched with acks in explicit
way.

This also enables re-open attempts in all the aptly commands, so it
should make running aptly CLI much easier now hopefully.

Fix up system tests for oldoldstable ;)

context/context.go

@@ -3,6 +3,7 @@ package context
 
 import (
 	"fmt"
+	"math/rand"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -238,13 +239,34 @@ func (context *AptlyContext) _database() (database.Storage, error) {
 	if context.database == nil {
 		var err error
 
-		context.database, err = database.OpenDB(context.dbPath())
+		context.database, err = database.NewDB(context.dbPath())
 		if err != nil {
-			return nil, fmt.Errorf("can't open database: %s", err)
+			return nil, fmt.Errorf("can't instanciate database: %s", err)
 		}
 	}
 
-	return context.database, nil
+	tries := context.flags.Lookup("db-open-attempts").Value.Get().(int)
+	const BaseDelay = 10 * time.Second
+	const Jitter = 1 * time.Second
+
+	for ; tries >= 0; tries-- {
+		err := context.database.Open()
+		if err == nil || !strings.Contains(err.Error(), "resource temporarily unavailable") {
+			return context.database, err
+		}
+
+		if tries > 0 {
+			delay := time.Duration(rand.NormFloat64()*float64(Jitter) + float64(BaseDelay))
+			if delay < 0 {
+				delay = time.Second
+			}
+
+			context._progress().Printf("Unable to open database, sleeping %s, attempts left %d...\n", delay, tries)
+			time.Sleep(delay)
+		}
+	}
+
+	return nil, fmt.Errorf("unable to reopen the DB, maximum number of retries reached")
 }
 
 // CloseDatabase closes the db temporarily
@@ -261,26 +283,9 @@ func (context *AptlyContext) CloseDatabase() error {
 
 // ReOpenDatabase reopens the db after close
 func (context *AptlyContext) ReOpenDatabase() error {
-	context.Lock()
-	defer context.Unlock()
+	_, err := context.Database()
 
-	if context.database == nil {
-		return nil
-	}
-
-	const MaxTries = 10
-	const Delay = 10 * time.Second
-
-	for try := 0; try < MaxTries; try++ {
-		err := context.database.ReOpen()
-		if err == nil || !strings.Contains(err.Error(), "resource temporarily unavailable") {
-			return err
-		}
-		context._progress().Printf("Unable to reopen database, sleeping %s\n", Delay)
-		<-time.After(Delay)
-	}
-
-	return fmt.Errorf("unable to reopen the DB, maximum number of retries reached")
+	return err
 }
 
 // CollectionFactory builds factory producing all kinds of collections