Allow setHostWeight() to work before cluster is started.

[AltSysrq]

Currently, it requires starting the cluster first, which makes configuration
needlessly awkward:

1. Configure the driver
2. Obtain at least one connection
3. Finish configuring the driver

In our use case, configuration is handled by a shared library, but when the
connection gets created is not under that library's control, so there's not
even an opportunity to call 3.

This modifies setHostWeight() to not fail if called bofer clusters have been
initialised, and instead stores the configured weight in a static map. As new
clusters are created, they pull weights from that map when they have a matching
server.

[jentfoo]

LGTM, good idea. We need to update the version to 0.15-SNAPSHOT here https://github.com/threadly/auroraArc/blob/master/gradle.properties#L2 before I can merge. I can do this in master before hand if you don't want to.

[AltSysrq]

Pushed a bump to that version.

[jentfoo]

This should be available in maven central as 0.15 now

[AltSysrq]

@jentfoo Looks like only arcCommon was uploaded again — since nothing in the mysql module has changed since 0.13 it's not an immediate problem for me though

[jentfoo]

I double checked that they were included in the bundle being published. I wonder if maven is optimizing to not release versions with matching hashes?

Thanks for letting me know, that is a good point that 0.13 can be used otherwise.