shell: Disable the "Previous" button appropriately

Fixes #425
Closes #891
Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Disable the "Next" button appropriately

Disable the "Next" button when the address or host name is empty.
When the address or host name is incorrect, the button is disabled,
but still freezed, this will be fixed together with the returned
error issue.

When the button is freezed, it will change back to the enabled
state whenever the address is altered.

The address text input will get the focus when the "address" tab
shows up.

Fixes #861
Closes #892
Reviewed-by: Stef Walter <stefw@redhat.com>
ws: Minor whitespace formatting tweak

Format change about the previous commit

Reviewed-by: Stef Walter <stefw@redhat.com>
shell: No need to show "login" tab

No need to show "login" tab when clicking "previous" button
if the "reuse creds" label is checked in the "address" tab.

Closes #894
Reviewed-by: Stef Walter <stefw@redhat.com>
shell: Keep the behavior consistent.

Make the behavior of input text in the "Add Server" tab is the
same as the login screen. Pressing Enter Key now in the "address"
and "login" tabs are the same as clicking the button.

Closes #896
Reviewed-by: Stef Walter <stefw@redhat.com>
Add more autofoo cruft to .gitignore
common: Run spawned commands from $PATH

This makes us less fragile, when commands move between
directories.
shell: Use $PATH when executing various spawned commands

This will simplify porting efforts, between OS releases
and distros.

Closes #887