Tests for add and delete interface squashed in only one
Some tests shortened
Removed needless spaces
VLAN creation tests squashed in only one
VLAN creation and deletion tests squeezed into one single test
Tests reworked
Simplified VLAN parameter checks
Fixed running configuration for a test
Interface adding and deletion squeezed in only one test
VLAN creation, updating and deletion squeezed in only one test
Code cleanup and increased coverage