meta-phosphor: network: Add symlink to git

Add a symbolic link to network.bb named _git.bb and set the preferred
version for the recipe.

Change-Id: I4fbff3595f7070ddfde1f2b18d7203ee510717fe
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/conf/distro/include/phosphor-defaults.inc b/conf/distro/include/phosphor-defaults.inc
index 526108e..7d95900 100644
--- a/conf/distro/include/phosphor-defaults.inc
+++ b/conf/distro/include/phosphor-defaults.inc
@@ -246,3 +246,4 @@
 VIRTUAL-RUNTIME_phosphor-ipmi-providers ?= "phosphor-ipmi-fru"
 
 PREFERRED_VERSION_phosphor-gpio-monitor = "1.0"
+PREFERRED_VERSION_network = "1.0"