fix(GraphQL):This PR will fix the graphl tests that were failing because of recent change in dgraph.

[JatinDev543]

we have changed in Dgraph the way rollups are done in this PR. #7253
As a result of it, we were having below unexpected behavior in graphql while updating the schema.
issue:
suppose we send below schema requests,

1.schema1
2.schema2

Badger is supposed to return the following updates to graphql

1.schema1
1.schema1
1.schema1
2.schema2
2.schema2
2.schema2

If we get a schema update that is same as our previous schema then we are already ignoring that
in graphql.For example, below multiple updates for schema1,schema2 from badger gets ignored

1.schema1  //accepted,new update
2.schema1  //discarded,same as previous
3.schema1  //discarded,same as previous
4.schema1  //discared,same as previous
5.schema2  //accepted,new update 
6.schema2  //discarded,same as previous
7.schema2  //discarded,same as previous

But because of the recent change we are now sometimes getting older updates in random order like below.

1.schema1  //version1
2.schema2  //version2
3.schema1  //version1

so in this case graphql was assuming that we got an new schema which actually was old schema.
And due to that multiple errors were broken.

Solution
The solution is simple.Every update from the badger also have version associated to it.
And that version number is strictly increasing. Now, if we get an schema with version <= current schema version
then we don't update the graphql schema.And that solve the issue

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This change is 

[pawanrawal]

Reviewable status: 0 of 1 files reviewed, 1 unresolved discussion (waiting on @jatindevdg)

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graphql/admin/admin.go, line 540 at r1 (raw file):

		if newSchema.Version <= server.schema.Version || newSchema.Schema == server.schema.Schema {
			glog.Infof("Skipping GraphQL schema update because either we got same schema or schema with older" +
				" version than version of current schema ")

Skipping GraphQL schema update, new badger key version is %d, the old version was %d.

[JatinDev543]

Reviewable status: 0 of 2 files reviewed, 1 unresolved discussion (waiting on @manishrjain, @pawanrawal, and @vvbalaji-dgraph)

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graphql/admin/admin.go, line 540 at r1 (raw file):

Previously, pawanrawal (Pawan Rawal) wrote…

Skipping GraphQL schema update, new badger key version is %d, the old version was %d.

done.