Atest: fix single positional arg for --acloud-create

argparse treat '-*' as optional args rather than positional args. This
CL implement argparse.REMAINDER to accept anything after --acloud-create
as its optional args.

Bug: 158969405
Bug: 149365268

Test: before and after this CL
 #### before this CL:
 atest-dev hello_world_test -cv --acloud-create '--verbose'
 # atest will not create avd(args.acloud_create == None)
 atest-dev hello_world_test --acloud-create '--verbose '
 #atest will create avd(args.acloud_create=='--verbose ') with a
traillin space.

 ### after this CL:
 atest-dev hello_world_test -cv --acloud-create '--verbose'
 # will create an avd with acloud verbose mode.
 atest-dev hello_world_test --acloud-create
 # will not create avd.
 atest-dev --acloud-create hello_world_test
 # result in issuing 'acloud create hello_world_test', and fail.

Change-Id: I368dcb62ff93510d910f1ce8c1ae8245a57aab6e
2 files changed