tests: parametrize "sleep 1"

* tests/init.sh (SLEEP_A_BIT): New variable.
* tests/detach-sleeping: Use it.
* tests/detach-stopped: Likewise.
diff --git a/tests/detach-sleeping b/tests/detach-sleeping
index 8ea91e4..2a7e9ab 100755
--- a/tests/detach-sleeping
+++ b/tests/detach-sleeping
@@ -14,7 +14,7 @@
 while ! [ -s set_ptracer_any.out ]; do
 	kill -0 $! 2> /dev/null ||
 		fail_ 'set_ptracer_any sleep failed'
-	sleep 1
+	$SLEEP_A_BIT
 done
 rm -f set_ptracer_any.out
 
@@ -33,7 +33,7 @@
 while ! grep -F "Process $tracee_pid attached" $LOG > /dev/null; do
 	kill -0 $! 2> /dev/null ||
 		{ cat $LOG; cleanup; fail_ 'strace -p does not work'; }
-	sleep 1
+	$SLEEP_A_BIT
 done
 
 kill -INT $!
diff --git a/tests/detach-stopped b/tests/detach-stopped
index f837b04..3844fc2 100755
--- a/tests/detach-stopped
+++ b/tests/detach-stopped
@@ -14,7 +14,7 @@
 while ! [ -s set_ptracer_any.out ]; do
 	kill -0 $! 2> /dev/null ||
 		fail_ 'set_ptracer_any sleep failed'
-	sleep 1
+	$SLEEP_A_BIT
 done
 rm -f set_ptracer_any.out
 
@@ -34,13 +34,13 @@
 while ! grep -F "Process $tracee_pid attached" $LOG > /dev/null; do
 	kill -0 $! 2> /dev/null ||
 		{ cat $LOG; cleanup; fail_ 'strace -p does not work'; }
-	sleep 1
+	$SLEEP_A_BIT
 done
 
 while ! grep -F -e '--- stopped by ' $LOG > /dev/null; do
 	kill -0 $! 2> /dev/null ||
 		{ cat $LOG; cleanup; fail_ 'strace -p does not work'; }
-	sleep 1
+	$SLEEP_A_BIT
 done
 
 kill -INT $!
diff --git a/tests/init.sh b/tests/init.sh
index a3ff2f8..3976a1e 100644
--- a/tests/init.sh
+++ b/tests/init.sh
@@ -19,3 +19,4 @@
 
 : "${STRACE:=../strace}"
 : "${TIMEOUT_DURATION:=60}"
+: "${SLEEP_A_BIT:=sleep 1}"