suricata: build cifuzz only against master branch (google#11800)

cc @jonathanmetzman did I get it right ?

Author: catenacyber

projects/suricata/build.sh

@@ -86,7 +86,7 @@ then
 fi
 
 fuzz_branches=("")
-if [[ "$SANITIZER" != "memory" ]]
+if [[ "$SANITIZER" != "memory" ]] && [[ ! -v CIFUZZ ]]
 then
     fuzz_branches+=("6")
     fuzz_branches+=("7")
@@ -131,11 +131,6 @@ cat generic.dict >> $OUT/fuzz_applayerparserparse$branch.dict
 cat generic.dict >> $OUT/fuzz_sigpcap$branch.dict
 cat generic.dict >> $OUT/fuzz_sigpcap_aware$branch.dict
 
-df
-# clean to leave enough space for CIFuzz
-make clean
-df
-
 # build corpuses
 # default configuration file
 zip -r $OUT/fuzz_confyamlloadstring"$branch"_seed_corpus.zip suricata.yaml