can't import trigger dependencies that use logical operators

[discovered by sasha]

in 2.2: have a host or template with two triggers, where at least one uses a logical operator like | or &. have the other trigger depend on this this trigger. export this host/template

in 2.4: try to import this template. that fails with : "Trigger "a2" depends on trigger "a1", which does not exist."

regression, broken by ZBXNEXT-1782