Enable bluetooth if it is diasbled.

[petal]

Enable bluetooth before scan when it is disable in Android.

[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.

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[braveheart007]

fantastic pull request, hope to merge soon

[pauldemarco]

Hi @petal,

Thanks for the contribution. Before I take a look, please rebase and sign the CLA.