meta-phosphor: Don't overwrite INHERIT in conf

INHERIT is being overwritten rather than appended to in
openbmc-phosphor.conf as of 0a544b5f874e81a1c4579d3de113c176668b6c80.

Use override append syntax for obmc-phosphor-utils and add a space to
separate from preceding classes.

Fixes openbmc/openbmc#1095.

Signed-off-by: Xo Wang <xow@google.com>
Change-Id: Id8c3c2d9cbab9cd5e1f0eff3674ad28084816da6
diff --git a/conf/distro/openbmc-phosphor.conf b/conf/distro/openbmc-phosphor.conf
index 2460e70..b32bb04 100644
--- a/conf/distro/openbmc-phosphor.conf
+++ b/conf/distro/openbmc-phosphor.conf
@@ -50,6 +50,6 @@
 # TODO: openbmc/openbmc#12345 - Upgrade to pygobject-3.
 PREFERRED_VERSION_python-pygobject = "2.%"
 
-INHERIT = "obmc-phosphor-utils"
+INHERIT_append = " obmc-phosphor-utils"
 
 include conf/distro/include/openbmc-phosphor/${MACHINE}.inc