meta-phosphor: phosphor-snmp: Disable test

The `tests` should not compile when I built BMC, This is a convention
that we disable `tests` in Yocto builds.

Tested: built phosphor-snmp passes.

Signed-off-by: George Liu <liuxiwei@inspur.com>
Change-Id: I060be140e7fcab7609d8ef9d79bd01073df834d3
diff --git a/meta-phosphor/recipes-phosphor/network/phosphor-snmp_git.bb b/meta-phosphor/recipes-phosphor/network/phosphor-snmp_git.bb
index ae9df3d..1fff205 100644
--- a/meta-phosphor/recipes-phosphor/network/phosphor-snmp_git.bb
+++ b/meta-phosphor/recipes-phosphor/network/phosphor-snmp_git.bb
@@ -20,4 +20,8 @@
 inherit python3native
 inherit obmc-phosphor-dbus-service
 
+EXTRA_OEMESON = " \
+    -Dtests=disabled \
+    "
+
 DBUS_SERVICE:${PN} += "xyz.openbmc_project.Network.SNMP.service"