os-release: Remove --long from git describe

The --long was added to address the issue described in
openbmc/openbmc#1692 where a tag name may not have a '-' separator, ex:
v1.99.6. The parsing of the tag name would then fail. But the parsing
was recently refactored so it no longer fails, we can remove the extra
verbosity of the VERSION_ID field now.
In simplified form, the previous parsing:
  "version = versionList[0] + "-" + versionList[1]"
Current parsing that doesn't fail if versionList[1] doesn't exist:
  "versionList[0:2]"

Tested: Created a tag 2.10.99 and verified the build succeeded and
        the output of os-release reflected the change in the VERSION_ID:
ID=openbmc-witherspoon
NAME="Phosphor OpenBMC (Phosphor OpenBMC Project Reference Distro)"
VERSION="2.10.99"
VERSION_ID=2.10.99
PRETTY_NAME="Phosphor OpenBMC (Phosphor OpenBMC Project Reference Distro) 2.10.99"
BUILD_ID="2.10.99"
OPENBMC_TARGET_MACHINE="witherspoon"

Change-Id: I502c72a5c3bfd49913b34bbaa041086c11845421
Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
diff --git a/meta-phosphor/recipes-core/os-release/os-release.bbappend b/meta-phosphor/recipes-core/os-release/os-release.bbappend
index 5d4a4af..4c9e157 100644
--- a/meta-phosphor/recipes-core/os-release/os-release.bbappend
+++ b/meta-phosphor/recipes-core/os-release/os-release.bbappend
@@ -15,7 +15,7 @@
         bb.warn("Unexpected exception from 'git' call: %s" % e)
         pass
 
-VERSION_ID := "${@run_git(d, 'describe --dirty --long')}"
+VERSION_ID := "${@run_git(d, 'describe --dirty')}"
 VERSION = "${@'-'.join(d.getVar('VERSION_ID').split('-')[0:2])}"
 
 BUILD_ID := "${@run_git(d, 'describe --abbrev=0')}"