Fix the `repmgr witness --help` command where at the "Unregister" section the message shown was
```
"witness register" unregisters a witness node.
```
instead of
```
"witness unregister" unregisters a witness node.
```
GitHub #676.
Also create an actual event notification for both actions, rather
than just creating the event record.
This is presumably an oversight from the original conversion to
repmgr4 which no-one has noticed before.
Log the output of PQerrorStatus() in a couple of places where it was missing.
Additionally, always log the output of PQerrorStatus() starting with a blank
line, otherwise the first line looks like it was emitted by repmgr, and
it's harder to scan the error message.
Before:
[2019-03-20 11:24:15] [DETAIL] could not connect to server: Connection refused
Is the server running on host "localhost" (::1) and accepting
TCP/IP connections on port 5501?
could not connect to server: Connection refused
Is the server running on host "localhost" (127.0.0.1) and accepting
TCP/IP connections on port 5501?
After:
[2019-03-20 11:27:21] [DETAIL]
could not connect to server: Connection refused
Is the server running on host "localhost" (::1) and accepting
TCP/IP connections on port 5501?
could not connect to server: Connection refused
Is the server running on host "localhost" (127.0.0.1) and accepting
TCP/IP connections on port 5501?
Previously, if the witness server connection details were provided
to "repmgr witness register" rather than those of the primary server,
repmgr a) write the node record to the witness server rather than
the primary, and b) would loop indefinitely trying to copy the
node table to itself.
Addresses GitHub #538.
Previously, "repmgr witness register --dry-run" would attempt to check
for records in the nodes table, but that might not exist yet. Skip
that check if the repmgr extension is not yet installed.
Implements GitHub #513.
