add 'dialout' group for user-level access to /dev/ttyUSB\d

This is for developers to access to /dev/ttyUSB devices
created by CCD in chroot without root access.

BRANCH=b:125335747
BUG=none
TEST=ran profiles/base/accounts/display-accts.py which checks
consistency.

$ display-accts.py
GID    GROUP                      PASS USERS
...
19     cdrom                      !    cros-disks
20     dialout                    !
...

I put 19 as dialout gid, and ran display-accts.py to see consistency
check working.

$ display-accts.py
...
error: duplicate gid found: 19: cdrom, dialout

Change-Id: I99045174bb63ffaf8856c3f65b39e856ff67d0c1
Signed-off-by: Namyoon Woo <namyoon@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1447412
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
diff --git a/profiles/base/accounts/group/dialout b/profiles/base/accounts/group/dialout
new file mode 100644
index 0000000..0248ad1
--- /dev/null
+++ b/profiles/base/accounts/group/dialout
@@ -0,0 +1,3 @@
+group:dialout
+gid:20
+users: