Enable BMC patching from the /usr/local path

This commit enables patches from the /usr/local path by replacing
absolute paths to /usr/sbin or /usr/bin in every service file with
"/usr/bin/env ". Additionally, SyslogIdentifier is added to each
file to ensure that journal entries are still distinct.

In two cases, service files also had to change due to references
to ${{PATH}}, which doesn't work with /usr/bin/env. These
references - and the corresponding definitions - were changed to
${{DEVPATH}}.

Resolves openbmc/openbmc#2149

Change-Id: I12c5c6e5101eef6820b985a563313836250ff2c7
Signed-off-by: Michael Tritz <mtritz@us.ibm.com>
diff --git a/common/recipes-phosphor/gpio/phosphor-gpio-monitor/phosphor-gpio-presence@.service b/common/recipes-phosphor/gpio/phosphor-gpio-monitor/phosphor-gpio-presence@.service
index 7872ce6..758a21f 100644
--- a/common/recipes-phosphor/gpio/phosphor-gpio-monitor/phosphor-gpio-presence@.service
+++ b/common/recipes-phosphor/gpio/phosphor-gpio-monitor/phosphor-gpio-presence@.service
@@ -6,7 +6,8 @@
 
 [Service]
 EnvironmentFile={envfiledir}/obmc/gpio/phosphor-power-supply-%i.conf
-ExecStart={sbindir}/phosphor-gpio-presence --path=${{PATH}} --inventory=${{INVENTORY}} --key=${{KEY}} --name=${{NAME}}
+ExecStart=/usr/bin/env phosphor-gpio-presence --path=${{DEVPATH}} --inventory=${{INVENTORY}} --key=${{KEY}} --name=${{NAME}}
+SyslogIdentifier=phosphor-gpio-presence
 
 [Install]
 RequiredBy={SYSTEMD_DEFAULT_TARGET}