Environment in delete failed state was in progress forever

Deletion sessions were in 'deploying' state instead of 'deleting'.
Because of this such sessions could not be found by RPC result
processing code and remained in 'deploying' status causing UI
to display progress bar forever

Also there were 2 duplicate SessionStates enums in the code
and the second copy was outdated and didn't contained DELETING
status as well as other new session statuses. Because buggy code
was using that outdated enum it was necessary to merge both enums
into single declaration

Closes-Bug: #1386068
Cherry-pick: I852f1f3dd1051c7b40afaa2575a4335b0f3c3104
Change-Id: I852f1f3dd1051c7b40afaa2575a4335b0f3c3104