puppet-apt: Fix buggy access to caller_module_name.
puppet-apt: Fix buggy access to caller_module_name.

New versions of Puppet on Ubuntu bionic don't like this.

jackrzhang/zulip,shubhamdhama/zulip,kou/zulip,eeshangarg/zulip,zulip/zulip,shubhamdhama/zulip,tommyip/zulip,jackrzhang/zulip,dhcrzf/zulip,jackrzhang/zulip,synicalsyntax/zulip,dhcrzf/zulip,rht/zulip,andersk/zulip,kou/zulip,tommyip/zulip,punchagan/zulip,punchagan/zulip,kou/zulip,andersk/zulip,jackrzhang/zulip,synicalsyntax/zulip,hackerkid/zulip,shubhamdhama/zulip,shubhamdhama/zulip,rishig/zulip,andersk/zulip,rishig/zulip,punchagan/zulip,jackrzhang/zulip,brainwane/zulip,timabbott/zulip,dhcrzf/zulip,shubhamdhama/zulip,hackerkid/zulip,andersk/zulip,eeshangarg/zulip,timabbott/zulip,jackrzhang/zulip,zulip/zulip,zulip/zulip,kou/zulip,brainwane/zulip,dhcrzf/zulip,timabbott/zulip,timabbott/zulip,punchagan/zulip,rishig/zulip,rht/zulip,kou/zulip,tommyip/zulip,brainwane/zulip,zulip/zulip,synicalsyntax/zulip,jackrzhang/zulip,brainwane/zulip,punchagan/zulip,eeshangarg/zulip,showell/zulip,hackerkid/zulip,rht/zulip,showell/zulip,synicalsyntax/zulip,dhcrzf/zulip,shubhamdhama/zulip,rishig/zulip,timabbott/zulip,rishig/zulip,andersk/zulip,showell/zulip,hackerkid/zulip,timabbott/zulip,synicalsyntax/zulip,tommyip/zulip,showell/zulip,eeshangarg/zulip,eeshangarg/zulip,shubhamdhama/zulip,showell/zulip,andersk/zulip,tommyip/zulip,showell/zulip,hackerkid/zulip,brainwane/zulip,eeshangarg/zulip,punchagan/zulip,dhcrzf/zulip,rht/zulip,eeshangarg/zulip,zulip/zulip,zulip/zulip,andersk/zulip,rht/zulip,kou/zulip,brainwane/zulip,rishig/zulip,hackerkid/zulip,rht/zulip,brainwane/zulip,synicalsyntax/zulip,timabbott/zulip,tommyip/zulip,zulip/zulip,synicalsyntax/zulip,tommyip/zulip,showell/zulip,dhcrzf/zulip,rishig/zulip,hackerkid/zulip,rht/zulip,kou/zulip,punchagan/zulip