parameterize goal and cancel publisher queue size.

[tfoote]

Refiled from @rchevali ros/gencpp#15

In action_client.h (on lines 217 and 221) both goal_pub_ and cancel_pub_ are advertised with queue sizes of 1. This occasionally causes goals to be dropped. Could these queue sizes be configurable or at least increased?

[esteve]

I increased the sizes for both queues to 10, to match the Python side in d4e2d2e It should fix any issues you may have experienced, would you mind @rchevali having a look at it? Thanks.

[esteve]

I'm closing this ticket, increasing both queue sizes to 10 doesn't seem to break anything.