jobs: Fix osmo-ggsn GTP build option

As far as I understand, the variable is populated using the name field.
In openggsn build it matches, but it doesn't in osmo-ggsn.

Change-Id: Ifb1a630b77a8c2f442e26dbef8e608882e8f9a71

jobs/gerrit-verifications.yml

@@ -104,7 +104,7 @@
           cmd: './contrib/jenkins_bts_model.sh "$BTS_MODEL"'
 
       - osmo-ggsn:
-          a1_name: gtp-linux
+          a1_name: GTP
           a1: !!python/tuple [--enable-gtp-linux,--disable-gtp-linux]
           cmd: GTP="$GTP" ./contrib/jenkins.sh
 

jobs/master-builds.yml

@@ -117,7 +117,7 @@
           cmd: './contrib/jenkins_bts_model.sh "$BTS_MODEL"'
 
       - osmo-ggsn:
-          a1_name: gtp-linux
+          a1_name: GTP
           a1: !!python/tuple [--enable-gtp-linux,--disable-gtp-linux]
           cmd: GTP="$GTP" ./contrib/jenkins.sh
           trigger: master-osmo-sgsn