API/clone: do not overwrite global signal handlers

perls 'local' must be either used in front of each $SIG{...}
assignments or they must be put in a list, else it affects only the
first variable and the rest are *not* in local context.

This may cause weird behaviour where daemons seemingly do not get
terminating signals delivered correctly and thus may not shutdown
gracefully anymore.

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

PVE/API2/Qemu.pm

@@ -2532,7 +2532,10 @@ __PACKAGE__->register_method({
 		my $jobs = {};
 
 		eval {
-		    local $SIG{INT} = $SIG{TERM} = $SIG{QUIT} = $SIG{HUP} = sub { die "interrupted by signal\n"; };
+		    local $SIG{INT} =
+			local $SIG{TERM} =
+			local $SIG{QUIT} =
+			local $SIG{HUP} = sub { die "interrupted by signal\n"; };
 
 		    PVE::Storage::activate_volumes($storecfg, $vollist, $snapname);