Let OS choose free port in MembershipKeyTest.

Bug: 293982420
Test: CtsLibcoreTestCases
Change-Id: I31143ca85dd0ddc3ae47915f1741f24d39dec3c8
Merged-In: I31143ca85dd0ddc3ae47915f1741f24d39dec3c8
(cherry picked from commit 532038b985234d28f4b34c7b66289c18c9427391)
1 file changed