Add support for rancher authentication

Add support for rancher authentication

This commit adds a new mode to the rancher1_api module, which enables
the rancher local authentication (username/password).

There is an already predefined rancher admin user called 'admin' and
that is the account, which this mode modifies. Due to the complex
API and the fact that rancher 1.6 is soon to be obsoleted, this module
is going the simpler route and it is just editing this default admin
account instead of creating a completely arbitrary username/password
credentials. For that reason is using the 'account_id', which is unique
for all accounts and the default admin account of rancher has '1a1'.

As of now this module cannot handle changed password once the auth. is
enabled.

Change-Id: Iea8923c71bdb82267c966a00d62f0f43eb5adb76
Issue-ID: OOM-1734
Signed-off-by: Petr Ospalý <p.ospaly@partner.samsung.com>