+++ This bug was initially created as a clone of Bug #878129 +++

today, when moving between one main tab to another, the search query is being "reset" to the "default" search-query associated with each main tab. 
e.g. when selecting the Hosts main tab, search query will be "reset" to the Hosts' main-tab default search query, i.e. "Hosts:". 

the request here is: upon selection of main tab "x", update the search query to the last search query that was applied while on main tab "x". 

example:

- login to the application
- [VMs main tab is displayed by default, search query is "VMs:"]
- change search query to: "VMs: name = a". apply search. 
- [VMs main grid is filtered based on the newly-applied search query]
- select the Hosts main tab
- [Hosts main tab is displayed, search query is changed to "Hosts:"]
- change search query to: "Hosts: cluster = Default or cluster = b*". apply search. 
- [Hosts main grid is filtered based on the newly applied search query]
- select the VMs main grid
- [VMs main tab is displayed]
  - [** current results: search query is changed to "VMs:"]
  - [** expected results: search query is changed to the last VMs query: "VMs: name = a"]
- select the Hosts main grid
- [Hosts main tab is displayed]
  - [** current results: search query is changed to "Hosts:"]
  - [** expected results: search query is changed to: "Hosts: cluster = Default or cluster = b*"]

note:

only query texts in the System context (i.e. when the 'System' tree-node is selected in the System tree) need to be remembered. 
when going into the tree-context (i.e. selecting something other than System), 
need to retain the current behavior. same for the tags-tree context.