AWS account variable removed

Description

aws_account variable has been removed from AWS deployment.

This is done using aws_caller_identity provided already by terraform aws provider natively.
https://www.terraform.io/docs/providers/aws/d/caller_identity.html

Breaking changes

The usage of the salt formulas used in the installation might not work if old versions are used. This are the current and tested versions:

drbd-formula == 0.3.10
habootstrap-formula == 0.3.0
saphanabootstrap-formula == 0.5.0
sapnwbootstrap-formula == 0.2.5
prometheus-hanadb_exporter == 0.7.0
prometheus-ha_cluster_exporter == 1.0.0
prometheus-sap_host_exporter == -
iscsi-formula == 1.1.1
python-PyHDB == 0.3.5.dev
python-prometheus_client == 0.7.1
python-shaptools == 0.3.5
salt-shaptools == 0.3.2