Use more easily configurable timezone, remove /etc/timezone mounts from containers; closes pterodactyl/panel#2513

If this does not completely solve the issue in containers then we need to evaluate the image being used to determine what changes need to happen to the image itself to support the timezone.

ref pterodactyl/panel#2239
ref pterodactyl/panel#2329
ref pterodactyl/panel#2389

server/server.go

@@ -6,6 +6,7 @@ import (
 	"github.com/apex/log"
 	"github.com/pkg/errors"
 	"github.com/pterodactyl/wings/api"
+	"github.com/pterodactyl/wings/config"
 	"github.com/pterodactyl/wings/environment"
 	"github.com/pterodactyl/wings/environment/docker"
 	"github.com/pterodactyl/wings/events"
@@ -13,7 +14,6 @@ import (
 	"golang.org/x/sync/semaphore"
 	"strings"
 	"sync"
-	"time"
 )
 
 // High level definition for a server instance being controlled by Wings.
@@ -78,10 +78,8 @@ func (s *Server) Id() string {
 // Returns all of the environment variables that should be assigned to a running
 // server instance.
 func (s *Server) GetEnvironmentVariables() []string {
-	zone, _ := time.Now().In(time.Local).Zone()
-
 	var out = []string{
-		fmt.Sprintf("TZ=%s", zone),
+		fmt.Sprintf("TZ=%s", config.Get().System.Timezone),
 		fmt.Sprintf("STARTUP=%s", s.Config().Invocation),
 		fmt.Sprintf("SERVER_MEMORY=%d", s.MemoryLimit()),
 		fmt.Sprintf("SERVER_IP=%s", s.Config().Allocations.DefaultMapping.Ip),
@@ -90,6 +88,7 @@ func (s *Server) GetEnvironmentVariables() []string {
 
 eloop:
 	for k := range s.Config().EnvVars {
+		// Don't allow any environment variables that we have already set above.
 		for _, e := range out {
 			if strings.HasPrefix(e, strings.ToUpper(k)) {
 				continue eloop