Server migration enhancement.

[LaserKaspar]

Found the issue in the logs:

ERROR: [Jun 27 00:10:10.690] error while handling HTTP request error=environment/docker: failed to create container: Error response from daemon: Requested CPUs are not available - requested 2,14,11,23, available: 0-7 request_id=5fb4fd53-2fa3-4e2e-940a-79c3e5bcfaa5 status=500 url=/api/transfers

Stacktrace:
Error response from daemon: Requested CPUs are not available - requested 2,14,11,23, available: 0-7
environment/docker: failed to create container
github.com/pterodactyl/wings/environment/docker.(*Environment).Create
        github.com/pterodactyl/wings/environment/docker/container.go:263
github.com/pterodactyl/wings/server.(*Server).CreateEnvironment
        github.com/pterodactyl/wings/server/server.go:276
github.com/pterodactyl/wings/router.postTransfers
        github.com/pterodactyl/wings/router/router_transfer.go:243
github.com/gin-gonic/gin.(*Context).Next
        github.com/gin-gonic/gin@v1.10.1/context.go:185
github.com/gin-gonic/gin.LoggerWithConfig.func1
        github.com/gin-gonic/gin@v1.10.1/logger.go:249
github.com/gin-gonic/gin.(*Context).Next
        github.com/gin-gonic/gin@v1.10.1/context.go:185
github.com/pterodactyl/wings/router.Configure.AttachApiClient.func5
        github.com/pterodactyl/wings/router/middleware/middleware.go:51
github.com/gin-gonic/gin.(*Context).Next
        github.com/gin-gonic/gin@v1.10.1/context.go:185
github.com/pterodactyl/wings/router.Configure.AttachServerManager.func4
        github.com/pterodactyl/wings/router/middleware/middleware.go:42
github.com/gin-gonic/gin.(*Context).Next
        github.com/gin-gonic/gin@v1.10.1/context.go:185
github.com/pterodactyl/wings/router/middleware.SetAccessControlHeaders.func1
        github.com/pterodactyl/wings/router/middleware/middleware.go:135
github.com/gin-gonic/gin.(*Context).Next
        github.com/gin-gonic/gin@v1.10.1/context.go:185
github.com/pterodactyl/wings/router.Configure.CaptureErrors.func3
        github.com/pterodactyl/wings/router/middleware/middleware.go:68
github.com/gin-gonic/gin.(*Context).Next
        github.com/gin-gonic/gin@v1.10.1/context.go:185
github.com/pterodactyl/wings/router.Configure.AttachRequestID.func2
        github.com/pterodactyl/wings/router/middleware/middleware.go:33
github.com/gin-gonic/gin.(*Context).Next
        github.com/gin-gonic/gin@v1.10.1/context.go:185
github.com/gin-gonic/gin.CustomRecoveryWithWriter.func1
        github.com/gin-gonic/gin@v1.10.1/recovery.go:102
github.com/gin-gonic/gin.(*Context).Next
        github.com/gin-gonic/gin@v1.10.1/context.go:185
github.com/gin-gonic/gin.(*Engine).handleHTTPRequest
        github.com/gin-gonic/gin@v1.10.1/gin.go:644
github.com/gin-gonic/gin.(*Engine).ServeHTTP
        github.com/gin-gonic/gin@v1.10.1/gin.go:600
net/http.serverHandler.ServeHTTP
        net/http/server.go:3301
net/http.(*conn).serve
        net/http/server.go:2102
runtime.goexit
        runtime/asm_amd64.s:1700

Would be nice if this could be checked before transfer/be displayed in the web-panel logs instead of failing for no reason.