(PUP-2958) Reclaim stale ssl lockfiles

[joshcooper]

Previously, puppet's ssl state machine would fail to run if the ssl lockfile
existed, no matter what it's contents were. Change the state machine to use
Puppet::Util::Pidlock instead which is capable of detecting if the pid refers
to an already running puppet instance.

[joshcooper]

Acquires empty lockfile:

[root@rllkgfa3qeth9t6 ~]# touch /etc/puppetlabs/puppet/ssl/ssl.lock
[root@rllkgfa3qeth9t6 ~]# puppet agent -t --certname something
Info: csr_attributes file loading from /etc/puppetlabs/puppet/csr_attributes.yaml
Info: Creating a new SSL certificate request for something
Info: Certificate Request fingerprint (SHA256): CC:DE:BF:B5:AA:52:EE:6B:9A:58:BE:AE:D5:9E:C2:E5:B5:6F:21:4F:BB:C4:C7:9F:A2:E8:95:8C:35:0C:A3:BC
Info: Certificate for something has not been signed yet
Couldn't fetch certificate from CA server; you might still need to sign this agent's certificate (something). Exiting now because the waitforcert setting is set to 0.

Acquires lockfile containing non-puppet pids:

[root@rllkgfa3qeth9t6 ~]# ps -p 1
  PID TTY          TIME CMD
    1 ?        00:00:01 systemd
[root@rllkgfa3qeth9t6 ~]# echo 1 > /etc/puppetlabs/puppet/ssl/ssl.lock
[root@rllkgfa3qeth9t6 ~]# puppet agent -t --certname something
Info: Creating a new RSA SSL key for something
Info: csr_attributes file loading from /etc/puppetlabs/puppet/csr_attributes.yaml
Info: Creating a new SSL certificate request for something
Info: Certificate Request fingerprint (SHA256): CC:DE:BF:B5:AA:52:EE:6B:9A:58:BE:AE:D5:9E:C2:E5:B5:6F:21:4F:BB:C4:C7:9F:A2:E8:95:8C:35:0C:A3:BC
Info: Certificate for something has not been signed yet
Couldn't fetch certificate from CA server; you might still need to sign this agent's certificate (something). Exiting now because the waitforcert setting is set to 0.

Faills to acquire when pid references background puppet process:

[root@rllkgfa3qeth9t6 ~]# systemctl start puppet
[root@rllkgfa3qeth9t6 ~]# pgrep puppet
26036
[root@rllkgfa3qeth9t6 ~]# echo 26036 > /etc/puppetlabs/puppet/ssl/ssl.lock
[root@rllkgfa3qeth9t6 ~]# puppet agent -t --certname something
Error: Could not run: Another puppet instance is already running; exiting