Description of problem:

The "streaming" behavior of docker events with --since option, changes if running under tty/pty.  Without the --events option, it always "streams" events as they happen untill the command is killed (expected).  However, if there is no pty/tty, and --since is used, the command exits after outputing past events (unexpected).  When a pty/tty is in control, the past events are output, then events "stream" until the process is killed.

Version-Release number of selected component (if applicable):
docker-0.11.1-19.el7.x86_64

How reproducible:
Easy

Steps to Reproduce:
1. docker events
2. echo "$(docker events)"
3. docker events --since=0
4. echo "$(docker events --since=0)"

Actual results:
#1 and #2 match in output + behavior (i.e. "stream" until killed)
#3 and #4 do NOT match (i.e. output and streaming behavior differ)

Expected results:
#3 and #4 should output and behavior should match.  Preferably "streaming" events, as #1 and #2 do - though 'help' text does not specify.

Additional info:
This is a regression from previous behavior (IIRC, before bug 1095901 was fixed).

An alternative fix could be fixing behavior of --since with a tty/pty, so it always exits after displaying prior events.  The downside would be, for "things" following events output, some could be lost between end of streaming past, and beginning of streaming new.  e.g.  docker events --since=0 > logfile && docker events >> logfile

Found on RHEL 7 GA using Autotest 0.16.0-master-63-g35e93, Docker test 0.7.4, "docker_cli/events" sub-test.