Improve handling of PostgreSQL output during "standby switchover"

Adapted from suggestion by GitHub user "ikusimakusi":

  https://github.com/2ndQuadrant/repmgr/pull/268

README.md

@@ -1084,11 +1084,6 @@ should have been updated to reflect this:
   the `repmgrd` may try and promote a standby by itself.
 - Any other standbys attached to the old master will need to be manually
   instructed to point to the new master (e.g. with `repmgr standby follow`).
-- You must ensure that following a server start using `pg_ctl`, log output
-  is not send to STDERR (the default behaviour). If logging is not configured,
-  we recommend setting `logging_collector=on` in `postgresql.conf` and
-  providing an explicit `-l/--log` setting in `repmgr.conf`'s `pg_ctl_options`
-  parameter.
 
 We hope to remove some of these restrictions in future versions of `repmgr`.
 

repmgr.c

@@ -8423,17 +8423,12 @@ remote_command(const char *host, const char *user, const char *command, PQExpBuf
 	}
 	else
 	{
-		/*
+		while (fgets(output, MAXLEN, fp) != NULL)
-		 * When executed remotely, repmgr commands which execute pg_ctl (particularly
-		 * `repmgr standby follow`) will see the pg_ctl command appear to fail with a
-		 * non-zero return code when the output from the executed pg_ctl command
-		 * has nowhere to go, even though the command actually succeeds. We'll consume an
-		 * arbitrary amount of output and throw it away to work around this.
-		 */
-		int i = 0;
-		while (fgets(output, MAXLEN, fp) != NULL && i < 10)
 		{
-			i++;
+			if (!feof(fp))
+			{
+				break;
+			}
 		}
 	}