fixes to database secrets engine

[drewmullen]

fix delete_connection return value. call does not return json object

include optional mount_point but default to 'database'

tested:
list_connections
read_connection
configure
delete_connection
create_role
delete_role
list_roles

[codecov-io]

Codecov Report

Merging #457 into develop will increase coverage by <.01%.
The diff coverage is 47.61%.

@@            Coverage Diff            @@
##           develop   #457      +/-   ##
=========================================
+ Coverage       88%    88%   +<.01%     
=========================================
  Files           50     50              
  Lines         2659   2660       +1     
=========================================
+ Hits          2340   2341       +1     
  Misses         319    319

Impacted Files	Coverage Δ
hvac/api/secrets_engines/database.py	37.5% <47.61%> (+1.6%)	⬆️

[drewmullen]

@jeffwecan alright so afaik these are good to go. ive tested most of the functionality and am using them here: TerryHowe/ansible-modules-hashivault#133

if you have a chance to merge and cut a release next week that would be AWESOME!

[jeffwecan]

Sounds good, thanks again for all the contributions! I'll aim to cut a release over the next few days as I have time available.

[drewmullen]

Absolutely. I'm looking at your unit tests trying to see if i can figure out a way to make some for this module also... havent messed with mocks much so might take me sometime but... its on the way!