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##### SUMMARY
<!--- Explain the problem briefly below, add suggestions to wording or structure -->
The [PSRP documentation](https://docs.ansible.com/ansible/latest/plugins/connection/psrp.html) mentions `ansible_psrp_connection_backoff` but this seems to be incorrect. The code appears to refer to `ansible_psrp_reconnection_backoff` instead (`reconnection` vs `connection`).
<!--- HINT: Did you know the documentation has an "Edit on GitHub" link on every page ? -->

##### ISSUE TYPE
- Documentation Report

##### COMPONENT NAME
<!--- Write the short name of the rst file, module, plugin, task or feature below, use your best guess if unsure -->
PSRP
lib/ansible/plugins/connection/psrp.py

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
ansible 2.8.0.dev0
  config file = /etc/ansible/ansible.cfg
  configured module search path = [u'/root/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/local/lib/python2.7/dist-packages/ansible-2.8.0.dev0-py2.7.egg/ansible
  executable location = /usr/local/bin/ansible
  python version = 2.7.15rc1 (default, Nov 12 2018, 14:31:15) [GCC 7.3.0]
```

##### CONFIGURATION
<!--- Paste verbatim output from "ansible-config dump --only-changed" between quotes -->
```paste below
None
```

##### OS / ENVIRONMENT
<!--- Provide all relevant information below, e.g. OS version, browser, etc. -->
Linux, Ubuntu 18.04.2 LTS

##### ADDITIONAL INFORMATION
<!--- Describe how this improves the documentation, e.g. before/after situation or screenshots -->
None.
<!--- HINT: You can paste gist.github.com links for larger files -->
cert_validation = self.get_option('cert_validation')
        cert_trust_path = self.get_option('ca_cert')
        if cert_validation == 'ignore':
            self._psrp_cert_validation = False
        elif cert_trust_path is not None:
            self._psrp_cert_validation = cert_trust_path
        else:
            self._psrp_cert_validation = True
        self._psrp_connection_timeout = self.get_option('connection_timeout')  
        self._psrp_read_timeout = self.get_option('read_timeout')  
        self._psrp_message_encryption = self.get_option('message_encryption')
        self._psrp_proxy = self.get_option('proxy')
        self._psrp_ignore_proxy = boolean(self.get_option('ignore_proxy'))
        self._psrp_operation_timeout = int(self.get_option('operation_timeout'))
        self._psrp_max_envelope_size = int(self.get_option('max_envelope_size'))
        self._psrp_configuration_name = self.get_option('configuration_name')
        self._psrp_reconnection_retries = int(self.get_option('reconnection_retries'))
        self._psrp_reconnection_backoff = float(self.get_option('reconnection_backoff'))
        self._psrp_certificate_key_pem = self.get_option('certificate_key_pem')
        self._psrp_certificate_pem = self.get_option('certificate_pem')
        self._psrp_credssp_auth_mechanism = self.get_option('credssp_auth_mechanism')
        self._psrp_credssp_disable_tlsv1_2 = self.get_option('credssp_disable_tlsv1_2')
        self._psrp_credssp_minimum_version = self.get_option('credssp_minimum_version')
        self._psrp_negotiate_send_cbt = self.get_option('negotiate_send_cbt')
        self._psrp_negotiate_delegate = self.get_option('negotiate_delegate')
        self._psrp_negotiate_hostname_override = self.get_option('negotiate_hostname_override')
        self._psrp_negotiate_service = self.get_option('negotiate_service')
        supported_args = []
        for auth_kwarg in AUTH_KWARGS.values():