tui: don't abort install if min ram requirement is not met

tui: don't abort install if min ram requirement is not met

If the minimum requirements are not met, the TUI installer will create a
popup notifying you that the install might not work and then exits the
installer.
While the GUI also creates such a popup, it will not exit the installer.
This patch adapts the behavior of the GUI: the TUI creates a popup
warning you that min spec is not met but doesn't abort the install.

Signed-off-by: Noel Ullreich <n.ullreich@proxmox.com>
Reviewed-by: Christoph Heiss <c.heiss@proxmox.com>
Tested-by: Christoph Heiss <c.heiss@proxmox.com>
 [T: fix conflict in context and drop intermediate variable ]
Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>