attempt to fix role::cache::mobile on labs

puppet on deployment-cache-mobile01 errors out while attempting to mount
/dev/sda3 and /dev/sdb3 which does not exist and should not even be
used.  Maybe the last members of a ternary like operator requires a
trailing comma.

The two errors are:

err:
/Stage[main]/Role::Cache::Mobile/Varnish::Setup_filesystem[sda3]/Mount[/srv/sda3]:
Could not evaluate: Execution of '/bin/mount -o
noatime,nodiratime,nobarrier,logbufs=8 /srv/sda3' returned 32: mount:
special device /dev/sda3 does not exist

err:
/Stage[main]/Role::Cache::Mobile/Varnish::Setup_filesystem[sdb3]/Mount[/srv/sdb3]:
Could not evaluate: Execution of '/bin/mount -o
noatime,nodiratime,nobarrier,logbufs=8 /srv/sdb3' returned 32: mount:
special device /dev/sdb3 does not exist

Change-Id: I22fa0086703bb5952eff36b8e7662558211aefb4