Bump swap to 3GB in linuxbridge and openvswitch jobs

Since [1] linuxbridge and openvswitch jobs are randomly
failing as swap gets fully utilized and processes are
getting oom-killed, to avoid this increasing swap size
to 3GB.

[1] https://review.opendev.org/c/openstack/devstack/+/924094

Closes-Bug: #2073582
Change-Id: I3889beb4c3427dd14ba1d1cddc9027b366268c1b

zuul.d/master_jobs.yaml

@@ -235,7 +235,7 @@
     parent: neutron-tempest-plugin-base-nested-switch
     timeout: 10000
     vars:
-      configure_swap_size: 2048
+      configure_swap_size: 3072
       devstack_services:
         # Disable OVN services
         br-ex-tcpdump: false
@@ -341,7 +341,7 @@
     parent: neutron-tempest-plugin-base-nested-switch
     timeout: 10000
     vars:
-      configure_swap_size: 2048
+      configure_swap_size: 3072
       devstack_services:
         # Disable OVN services
         br-ex-tcpdump: false
@@ -509,7 +509,7 @@
       - zuul: openstack/neutron
     pre-run: playbooks/linuxbridge-scenario-pre-run.yaml
     vars:
-      configure_swap_size: 2048
+      configure_swap_size: 3072
       devstack_services:
         # Disable OVN services
         br-ex-tcpdump: false