Bug 1075186

Description of problem:

When editing a VM template, "Use custom migration downtime" in Host section is initially always unchecked and the text input is blank and writable at the same time.
This leads to form validation error when trying to submit the dialog without putting any value in the text input.
When "Use custom migration downtime" is checked and some value is entered, this value is correctly saved to DB (could be checked via REST API), but next time Edit Template dialog is opened, the situation repeats as above.

Version-Release number of selected component (if applicable):
rhevm-3.4.0-0.3.master.el6ev.noarch (av2.1)

How reproducible:
100%

Steps to Reproduce:
1. Create new template from VM, which has set "Use custom migration downtime" to 125.
2. Check the template via REST API - it should contain <migration_downtime>125</migration_downtime>
3. Edit the template and go to Host side-tab.
 a. Check the state and value of "Use custom migration downtime"
 b. Just submit the dialog without changing anything there.

Actual results:
3a. The checkbox is unchecked, yet the text input is writable; and always blank.
3b. Related to 3a. Cannot submit the dialog, a value is required to be entered in the text input even when the checkbox is unchecked. (see attached screenshot)

Expected results:
3a. The checkbox is checked/unchecked depending on the saved value in DB. Also if unchecked, the text input should be disabled/read-only.
3b. Dialog is submitted successfully.

Additional info:

There are basically two problems in the GUI:
1. The text input never shows the value stored in DB.
2. The logic between the checkbox and text input is not correct when the dialog is initially loaded (checkbox is unchecked & text input is writable -> wrong).