The option --bidirectional for --set-sync/--set-async works only from master

[trivadis]

The option --bidirectional for --set-sync/--set-async works only from master

[rolandstirnimann]

Fixed. The following test is executed on the current standby node.

$ ### Check setting on master
$ ssh vmpg153rz43ha "grep synchronous_standby_names $TVD_PGCONF"
synchronous_standby_names = ''          # Modified by PgOperate

$ ### Check setting on standby
$ grep synchronous_standby_names $TVD_PGCONF
synchronous_standby_names = ''          # Modified by PgOperate

$ pgoperate --standbymgr --set-sync --target olt --bidirectional

$ ### Check setting on master
$ ssh vmpg153rz43ha "grep synchronous_standby_names $TVD_PGCONF"
synchronous_standby_names = 'olt'               # Modified by PgOperate

$ ### Check setting on standby
$ grep synchronous_standby_names $TVD_PGCONF
synchronous_standby_names = 'zhh'               # Modified by PgOperate