samples: mgmt: mcumgr: smp_svr: Bluetooth advertising restarted on connection

[nordicjm]

Describe the bug
Commit c6ad4a7 introduced an error whereby after a device connects, bluetooth advertising is restarted irrespective if the connection was successful or not, this leads to an error if the connection was successful since the maximum number of connections in the sample is 1 and it cannot hold a connection and be advertising for another one.

Expected behavior
Advertising not restarted if the connection was successful

Impact
Annoyance

Environment (please complete the following information):

• Commit SHA or Version used: 29208fe present in 3.7 and 4.0