Store correct session duration

[nymous]

What happened:

When connecting to a host through sshportal, an entry is created in the sessions table. But all connections are shown as "Closed" immediately, and the stopped_at column is set to the same value as the created_at.

What you expected to happen:

sshportal saves the timestamp when the connection closes.

How to reproduce it (as minimally and precisely as possible):

1. Setup sshportal with a user and a host
2. Connect to the host
3. In another terminal, run session ls in sshportal
4. Session is marked as "Closed", with a 1s duration

Environment:

• sshportal --version: sshportal version 1.8.0+dev ()
• sshportal info:

debug mode (server): false
Hostname: bastion
CPUs: 4
Demo mode: false
DB Driver: mysql
DB Conn: REDACTED@tcp(localhost:3306)/sshportal?charset=utf8&parseTime=true&loc=Local
Bind Address: :2222
System Time: 2018-06-26T14:22:35.351678631Z
OS Type: linux
OS Architecture: amd64
Go routines: 2275
Go version (build): go1.8.3
Uptime: 1302h33m53.669240829s
User ID: 4
User email: REDACTED
Version: 1.8.0+dev
GIT SHA:
GIT Branch:
GIT Tag:

• OS: CentOS 7.4.1708
• install method: go
• installed with a MySQL DB to store data

[moul]

fixed by #75