Plan environment file is not being sourced after prepare and execute in tmt-try

[xduda]

The documentation states file located at TMT_PLAN_ENVIRONMENT_FILE should be sourced after steps prepare and execute.
When running from tmt try, this doesn't happen.

Steps to reproduce:

/plan:

provision:
    how: local
discover:
    how: fmf
prepare:
    how: shell
    script: echo "VAR=hello" >> $TMT_PLAN_ENVIRONMENT_FILE
execute:
    how: tmt

/test:

framework: shell
test: test "${VAR}" = "hello"

the plan succeeds when running tmt run plans -n plan,
but fails when running as tmt try -p plan