Ability to set swap size per host as a variable

[Kushmaro]

We'd like to allow customers to configure the amount of swap defined on each ECE host, instead of always using a predetermined formula as seen here

The formula should act as a default, but there may be some cases where 7% of disk space is too little or too much from a customers' perspective.

[Kushmaro]

/cc @deepybee as discussed

[deepybee]

I have this and a bunch of additional improvements to get sorted, planning on attacking en masse next week.