magfield.tcl: introduce timeout for ramp to fielf

tcl/drivers/magfield.tcl

@@ -247,8 +247,13 @@ proc magfield::run {} {
     if {[sct phase] != 0 || abs($tf - $pf) > $tol || $pm != 1} {
       # we have to go to persistent field
       if {![sct leads_at_field]} {
+        if {[sct phase] == 2 &&  $now > [silent $now sct start_phase2] + 300} {
+          sct phase 1
+          clientlog "timeout ramping to persistent field -> redo"
+        }
         if {[sct phase] < 2} {
           sct phase 2 ;# ramping leads to field 
+          sct start_phase2 $now
           msg "ramp to persistent field $pf"
           lassign [check_field $pf] ok
           if {!$ok} {