Reorder WaitForDBAGrants to call to ensure it runs before MySQL restore

[GuptaManan100]

Description

This PR tries to fix the issue pointed out in #14834.
This is an extension of #14565 and #14680.

We reorder the WaitForDBAGrants such that it runs before we start restoring mysql for the case when the vttablets are running with restore_from_backup flag. There is virtually no difference for the case when the given flag is false.

This change ensures that we have verified and waited for the users to have the correct grants when we start serving RPC calls.

Related Issue(s)

• Fixes Bug Report: RPCs to a new started VTTablet sometimes fail #14834

Checklist

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[vitess-bot]

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[GuptaManan100]

These changes will reintroduce the problem in #14681. We'll have to find an alternate fix.