refactor(systemd): clean up paths

harcoded paths are not required in shell environments. I've also
removed unnecessary uses of /bin/sh when we only require an
environment variable, since systemd can reference environment
variables through ${}.

ref: http://www.freedesktop.org/software/systemd/man/systemd.service.html#ExecStart=

Author: Matthew Fisher

scheduler/coreos.py

@@ -199,10 +199,10 @@ def attach(self, name):
 [Service]
 ExecStartPre=/usr/bin/docker pull {image}
 ExecStartPre=/bin/sh -c "docker inspect {name} >/dev/null 2>&1 && docker rm -f {name} || true"
-ExecStart=-/usr/bin/docker run --name {name} -P -e PORT={port} {image} {command}
-ExecStartPost=-/bin/sh -c "until docker inspect {name} >/dev/null 2>&1; do sleep 1; done"; \
-    -/bin/sh -c "arping -Idocker0 -c1 `docker inspect -f '{{{{ .NetworkSettings.IPAddress }}}}' {name}`"
-ExecStop=-/usr/bin/docker rm -f {name}
+ExecStart=/usr/bin/docker run --name {name} -P -e PORT={port} {image} {command}
+ExecStartPost=/bin/sh -c "until docker inspect {name} >/dev/null 2>&1; do sleep 1; done"; \
+    /bin/sh -c "arping -Idocker0 -c1 `docker inspect -f '{{{{ .NetworkSettings.IPAddress }}}}' {name}`"
+ExecStop=/usr/bin/docker rm -f {name}
 """
 
 ANNOUNCE_TEMPLATE = """

systemd/deis-controller.service

@@ -6,9 +6,9 @@ After=deis-logger.service
 [Service]
 EnvironmentFile=/etc/environment
 TimeoutStartSec=20m
-ExecStartPre=/bin/sh -c "/usr/bin/docker history deis/controller >/dev/null || /usr/bin/docker pull deis/controller"
-ExecStartPre=/bin/sh -c "/usr/bin/docker inspect deis-controller >/dev/null && /usr/bin/docker rm -f deis-controller || true"
-ExecStart=/bin/sh -c "docker run --name deis-controller -p 8000:8000 -e PUBLISH=8000 -e HOST=$COREOS_PRIVATE_IPV4 --volumes-from=deis-logger deis/controller"
+ExecStartPre=/bin/sh -c "docker history deis/controller >/dev/null || docker pull deis/controller"
+ExecStartPre=/bin/sh -c "docker inspect deis-controller >/dev/null && docker rm -f deis-controller || true"
+ExecStart=/usr/bin/docker run --name deis-controller -p 8000:8000 -e PUBLISH=8000 -e HOST=${COREOS_PRIVATE_IPV4} --volumes-from=deis-logger deis/controller
 ExecStop=/usr/bin/docker rm -f deis-controller
 
 [Install]