btshell: Fix restarting advertising instances #1878

Job	Run time
Build GCC test target (ubuntu-latest, 10.3-2021.10)	2m 48s
Build GCC test target (ubuntu-latest, 14.2.Rel1)	2m 50s
Build GCC test target (ubuntu-latest, 11.3.Rel1)	3m 7s
Build GCC test target (ubuntu-latest, 9-2020-q2)	2m 57s
Build GCC test target (ubuntu-latest, 12.2.Rel1)	2m 56s
Build GCC test target (ubuntu-latest, 13.2.Rel1)	2m 35s
Build GCC test target (ubuntu-latest, 8-2019-q3)	3m 52s
	21m 5s

Provide feedback