Implementation of stopping/resetting env in Nailgun

Added implementation of environment resetting

Implements: blueprint nailgun-reset-env

Change-Id: Ib2c8d2f7f570ba4293f7930cf4837a7ec09e222b
Stop/Reset actions on UI

Change-Id: Ib2df1cf52a135bdac14e71a2684c3f54d3987620