[Integrated] RFR: Add Host::isMemberOf

[duke]

Changeset: 048a1c8a
Author:    Erik Helin <ehelin at openjdk.org>
Date:      2019-10-02 09:10:33 +0000
URL:       https://git.openjdk.java.net/skara/commit/048a1c8a

Add Host::isMemberOf

Reviewed-by: rwestberg

! host/src/main/java/org/openjdk/skara/host/Host.java
! host/src/main/java/org/openjdk/skara/host/github/GitHubHost.java
! host/src/main/java/org/openjdk/skara/host/gitlab/GitLabHost.java
+ host/src/test/java/org/openjdk/skara/host/HostTests.java
! test/src/main/java/org/openjdk/skara/test/TestHost.java