tests: few more tests for fake/custom IP
tests: few more tests for fake/custom IP

QubesOS/qubes-issues#1143
QubesOS/qubes-issues#1477

QubesOS/qubes-core-admin,marmarek/qubes-core-admin,QubesOS/qubes-core-admin,marmarek/qubes-core-admin,marmarek/qubes-core-admin,woju/qubes-core-admin,woju/qubes-core-admin,woju/qubes-core-admin,QubesOS/qubes-core-admin,woju/qubes-core-admin