populate googleSubjectId with current uid

[Qi77Qi]

After this, we should run migration, so that there won't be users missing googleSubjectId field before we change proxy

Discussion https://broadinstitute.slack.com/archives/CC528F8JX/p1535681551000100

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[gpolumbo-broad]

I approve it even though it doesn't make sense to me that the sn, cn also have the same value as the uid and googleSubjectId.

[Qi77Qi]

@gpolumbo-broad , I don't know much about sn and cn, but I think we should leave them as is for this PR.

The reason for duplicating googleSubjectId here is just so we can change proxy to lookup users by googleSubjectId. Code change in this PR will be updated in #190, but this PR allows us to change proxy without breaking anything in the mean time. It's 2 in https://broadinstitute.atlassian.net/wiki/spaces/~952052303/pages/622624856/sam+Support+invite+feature