Cancel download throw error bugfix (Android)

[CapitanRedBeard]

This PR is based on #363
In which @minextu wrote:

Moved from wkh237#568
Fixes #182

Original Description:

Issue wkh237#555 describes that aborting a download does not lead to promise rejection. This bug has been fixed so that both at Android and iOS the promise will be rejected.

Basically he found a working PR that was put up against the old wkh237 repo but was obviously out of date.

PR #363 has a couple of unnecessary commits attached to it so I've simply took the only commit that actually fixes the problem and made a new PR with that.

Tested this against iOS and Android and now both platform are throwing a catchable Error whenever you call .cancel() on fetch request as the documentation says it should

@Traviskn Can you review/merge this in when you get a chance, pretty harmless PR that fixes an old problem.

For anyone needing this functionality point to this repo/branch:

"rn-fetch-blob": "git+https://github.com/repodio/rn-fetch-blob.git#throw-on-cancel-android"

until this PR has been merged

[Traviskn]

Thank you for your PR, apologies for the delayed review