Add versionAllWithErrors to return info on which hosts succeeded or failed

[schleyfox]

versionAll throws on the first error it receives and does not include information on which host was responsible for the error. If the error is thrown quickly, the method will be stopped before other hosts have a chance to respond. Observers of the callbacks will view this as a host timeout.

versionAllWithErrors changes this to wait on all responses regardless of error status and return a map of servers containing either the returned version or the error. The callbacks are extended to also record the error case explicitly so that in a case where there is a timeout in the monitoring code before the method returns the observer can record partial success and specific errors.

[leon-root]

Is there any real error example?
Something like EConnectError?

[schleyfox]

In the test we use a non-error object for ease of equality checking (though I suppose we could just construct an Error object of our choosing)

Possible errors are:

memjs/src/memjs/utils.ts

Line 159 in c84319e

throw new Error("ERROR Too many open connections");

memjs/src/memjs/server.ts

Line 168 in c84319e

this.error(new Error("Memcached server authentication failed!"));

memjs/src/memjs/server.ts

Line 231 in c84319e

self.error(new Error("socket closed unexpectedly."));

memjs/src/memjs/server.ts

Line 251 in c84319e

self.error(new Error("socket timed out connecting to server."));

memjs/src/memjs/server.ts

Line 326 in c84319e

server.error(new Error("socket timed out waiting on response."));

any errors that socket can have (things like ECONNRESET, etc):

memjs/src/memjs/server.ts

Lines 225 to 227 in c84319e

	self._socket.on("error", function (error) {
	self.error(error);
	});

and whatever this is

memjs/src/memjs/memjs.ts

Line 945 in c84319e

this.createAndLogError("VERSION", response!.header.status)