Avoid duplicating warnings when reading table

Invalid lines in a file was the one case that would not suppress future
warnings. Just make it suppress warnings too, but clear that suppression
if there is a field in between that doesn't error.

Fixes #3692

testing/btest/Baseline/scripts.base.frameworks.input.invalid-lines-duplicate/.stderrwithoutfirstline

@@ -0,0 +1,5 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+warning: ..<...>/Input::READER_ASCII: ../input.log, line 3: Not enough fields in line 'hello' of ../input.log. Found 0 fields, want positions 1 and -1
+warning: ..<...>/Input::READER_ASCII: ../input.log, line 10: Not enough fields in line 'hello' of ../input.log. Found 0 fields, want positions 1 and -1
+received termination signal
+>>>

testing/btest/scripts/base/frameworks/input/invalid-lines-duplicate.zeek

@@ -0,0 +1,50 @@
+# @TEST-EXEC: btest-bg-run zeek zeek -b %INPUT
+# @TEST-EXEC: btest-bg-wait 10
+# @TEST-EXEC: sed 1d .stderr > .stderrwithoutfirstline
+# @TEST-EXEC: TEST_DIFF_CANONIFIER=$SCRIPTS/diff-remove-abspath btest-diff .stderrwithoutfirstline
+
+redef exit_only_after_terminate = T;
+redef InputAscii::fail_on_invalid_lines = F;
+
+@TEST-START-FILE input.log
+#fields	a	b	c
+#types	string	bool	bool
+hello
+hello
+hello
+hello
+hello
+hello
+"hi"	T	F
+hello
+hello
+hello
+hello
+hello
+hello
+hello
+@TEST-END-FILE
+
+type Key: record {
+    a: string;
+};
+
+type Val: record {
+    b: bool &log;
+    c: bool &log;
+};
+
+global test_table: table[string] of Val = table();
+
+event zeek_init() {
+    Input::add_table([
+        $source="../input.log", $name="test_table",
+        $idx=Key, $val=Val, $destination=test_table,
+        $mode=Input::REREAD
+    ]);
+}
+
+
+event Input::end_of_data(name: string, source:string) {
+	terminate();
+}