Fix method overwrite warnings in tests

[ararslan]

This happens because include is being called in a loop:

AWS.jl/test/runtests.jl

Lines 63 to 75 in d7e4dca

	backends = [AWS.HTTPBackend, AWS.DownloadsBackend]
	@testset "Backend: $(nameof(backend))" for backend in backends
	AWS.DEFAULT_BACKEND[] = backend()
	include("AWS.jl")
	include("IMDS.jl")
	include("AWSCredentials.jl")
	include("role.jl")
	include("issues.jl")
	if TEST_MINIO
	include("minio.jl")
	end
	end

Should be fixable by putting the tests for the different backends in their own module, e.g. have the loop body be something like

M = Module()
Core.include(M, "file1")
Core.include(M, "file2")

The annoying thing is just making sure that those modules load the packages they need and bring in things defined at the top level.