init: Fix and re-enable the init#StartConsole test

Skip the test if /dev/console does not exist. Fix the console service
security label. Fix the getsid() test.

Bug: 260104465
Test: atest 'CtsInitTestCases:init#StartConsole' on a P2023 development board
Change-Id: If2533a3f205f922a9b04a748cb558a09c5925986
Signed-off-by: Bart Van Assche <bvanassche@google.com>