tests/helper-runtests.sh

dirstate: infer the 'n' state from `from_p2`

This flag is only used with 'n' so lets set the state based on that parameter in
this case.

Differential Revision: https://phab.mercurial-scm.org/D10971

#
# Avoid interference from actual test env:

unset HGTEST_JOBS
unset HGTEST_TIMEOUT
unset HGTEST_PORT
unset HGTEST_SHELL