Do not check spark-bigdl.conf if sc exists (#1966)
Do not check spark-bigdl.conf if sc exists (#1966)

* do not check spark-bigdl.conf if sc exists

recover syspath

print warning instead exception if bigdl.conf doesn't exist

enhance unitest

remove warning

update test

try to fix jenkins

update

* delete

* fix

intel-analytics/BigDL,yangw1234/BigDL,yangw1234/BigDL,intel-analytics/BigDL,intel-analytics/BigDL,yangw1234/BigDL,intel-analytics/BigDL,yangw1234/BigDL