Avoid the unnecessary jobs when infer schema from list.

cc yhuai mengxr

Author: Davies Liu <davies@databricks.com>

Closes #6606 from davies/improve_create and squashes the following commits:

a5928bf [Davies Liu] Update MimaExcludes.scala
62da911 [Davies Liu] fix mima
bab4d7d [Davies Liu] Merge branch 'improve_create' of github.com:davies/spark into improve_create
eee44a8 [Davies Liu] Merge branch 'master' of github.com:apache/spark into improve_create
8d9292d [Davies Liu] Update context.py
eb24531 [Davies Liu] Update context.py
c969997 [Davies Liu] bug fix
d5a8ab0 [Davies Liu] fix tests
8c3f10d [Davies Liu] Merge branch 'master' of github.com:apache/spark into improve_create
6ea5925 [Davies Liu] address comments
6ceaeff [Davies Liu] avoid spark jobs in createDataFrame