Do not use `-rpcwait` on all `zcash_rpc` invocations, only block when starting zcashd.

qa/zcash/performance-measurements.sh

@@ -7,7 +7,7 @@ SHA256CMD="$(command -v sha256sum || echo shasum)"
 SHA256ARGS="$(command -v sha256sum >/dev/null || echo '-a 256')"
 
 function zcash_rpc {
-    ./src/zcash-cli -datadir="$DATADIR" -rpcwait -rpcuser=user -rpcpassword=password -rpcport=5983 "$@"
+    ./src/zcash-cli -datadir="$DATADIR" -rpcuser=user -rpcpassword=password -rpcport=5983 "$@"
 }
 
 function zcash_rpc_slow {
@@ -20,6 +20,10 @@ function zcash_rpc_veryslow {
     zcash_rpc -rpcclienttimeout=9000 "$@"
 }
 
+function zcash_rpc_wait_for_start {
+    zcash_rpc -rpcwait getinfo > /dev/null
+}
+
 function zcashd_generate {
     zcash_rpc generate 101 > /dev/null
 }
@@ -30,6 +34,7 @@ function zcashd_start {
     touch "$DATADIR/zcash.conf"
     ./src/zcashd -regtest -datadir="$DATADIR" -rpcuser=user -rpcpassword=password -rpcport=5983 -showmetrics=0 &
     ZCASHD_PID=$!
+    zcash_rpc_wait_for_start
 }
 
 function zcashd_stop {
@@ -44,6 +49,7 @@ function zcashd_massif_start {
     rm -f massif.out
     valgrind --tool=massif --time-unit=ms --massif-out-file=massif.out ./src/zcashd -regtest -datadir="$DATADIR" -rpcuser=user -rpcpassword=password -rpcport=5983 -showmetrics=0 &
     ZCASHD_PID=$!
+    zcash_rpc_wait_for_start
 }
 
 function zcashd_massif_stop {
@@ -59,6 +65,7 @@ function zcashd_valgrind_start {
     rm -f valgrind.out
     valgrind --leak-check=yes -v --error-limit=no --log-file="valgrind.out" ./src/zcashd -regtest -datadir="$DATADIR" -rpcuser=user -rpcpassword=password -rpcport=5983 -showmetrics=0 &
     ZCASHD_PID=$!
+    zcash_rpc_wait_for_start
 }
 
 function zcashd_valgrind_stop {