poky.conf: change case of Poky for DISTRO<->SANITY mismatch

Using anything build appliance based will emit the warning:

 WARNING: Host distribution "poky-1.7" has not been validated with
 this version of the build system; you may possibly experience
 unexpected failures. It is recommended that you use a tested distribution.

The chain of events leading to this is:

1) At image creation time:

   meta-yocto/conf/distro/poky.conf:
	DISTRO = "poky"

   meta/recipes-extended/lsb/lsb_4.1.bb:
	echo "DISTRIB_ID=${DISTRO}" >> ${D}${sysconfdir}/lsb-release

2) At deployment/usage time of the created image:

   meta/lib/oe/lsb.py:
	output, err = bb.process.run(['lsb_release', '-ir'], stderr=PIPE)

   meta-yocto/conf/distro/poky.conf:
	SANITY_TESTED_DISTROS ?= " \
            Poky-1.6 \n \
            Poky-1.7 \n \
            [...]

   meta/classes/sanity.bbclass:
	distro = oe.lsb.distro_identifier()
	tested_distros = sanity_data.getVar('SANITY_TESTED_DISTROS', True)

and hence the lsb.distro gets the lower case "poky" which fails to
match the upper case "Poky" used in SANITY_TESTED_DISTROS.

(From meta-yocto rev: 3373b04f8a61e5daa5d24501c0c7d8f947afb3f8)

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta-yocto/conf/distro/poky.conf

@@ -74,8 +74,8 @@ CONNECTIVITY_CHECK_URIS ?= " \
              http://bugzilla.yoctoproject.org/report.cgi"
 
 SANITY_TESTED_DISTROS ?= " \
-            Poky-1.6 \n \
-            Poky-1.7 \n \
+            poky-1.6 \n \
+            poky-1.7 \n \
             Ubuntu-12.04 \n \
             Ubuntu-14.04 \n \
             Ubuntu-14.10 \n \