dbcampaign: select multiple variants/benchmark pairs

The variant/benchmark selection now can use SQL LIKE syntax, all unfinished
pilots from all selected variants are sent to the clients. E.g.:

./cored-voter-server  -v x86-cored-voter -b simple-% -p basic

Will select the fsppilots in the variants:

- x86-cored-voter/simple-ip/basic
- x86-cored-voter/simple-instr/basic

The variant and benchmark information is now sent within the
fsppilot.

Change-Id: I287bfcddc478d0b79d89e156d6f5bf8188674532

src/core/comm/DatabaseCampaignMessage.proto

@@ -11,4 +11,6 @@ message DatabaseCampaignMessage {
     required int32 injection_instr          = 4 [(sql_ignore) = true];
     optional int32 injection_instr_absolute = 5 [(sql_ignore) = true];
     required int32 data_address             = 6 [(sql_ignore) = true];
+    required string variant                 = 7 [(sql_ignore) = true];
+    required string benchmark               = 8 [(sql_ignore) = true];
 }