samples: net: Do not setup VLAN if there is no VLAN interfaces #159909

Job	Run time
twister-build-prep / prep_push	1s
twister-build-prep / prep_pr	0s
twister-build (1)	1s
twister-build (2)	1s
twister-build (3)	1s
twister-build (4)	1s
twister-build (5)	1s
twister-build (6)	1s
twister-build (7)	1s
twister-build (8)	1s
twister-build (9)	1s
twister-build (10)	1s
twister-build (11)	1s
twister-build (12)	1s
twister-build (13)	1s
twister-build (14)	1s
twister-build (15)	1s
twister-build (16)	1s
twister-build (17)	1s
twister-build (18)	1s
twister-build (19)	1s
twister-build (20)	1s
Publish Unit Tests Results	1s
Check Twister Status / all jobs passed	1s
	23s

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