replace lockfile with mkdir (#406)

.travis/before_install.sh

@@ -54,10 +54,6 @@ cd /tmp || die
     [ $BUILD_TARGET != posix-32-bit ] || {
         sudo apt-get install g++-multilib || die
     }
-
-    [ $BUILD_TARGET != posix-distcheck ] || {
-        sudo apt-get install procmail || die
-    }
 }
 
 [ $TRAVIS_OS_NAME != osx ] || {

third_party/openthread-test-driver/test-driver

@@ -108,8 +108,7 @@ trap "st=143; $do_exit" 15
 lock_path="/tmp/offset"
 OFFSET=0
 while true; do
-    # using lockfile instead of mkdir since it's more portable
-    lockfile -0 -r 0 "${lock_path}.${OFFSET}.lock.d" > /dev/null 2>&1
+    mkdir "${lock_path}.${OFFSET}.lock.d" > /dev/null 2>&1
     if [ $? -eq 0 ]; then
         break
     fi
@@ -121,7 +120,7 @@ PORT_OFFSET=$OFFSET "$@" >$log_file 2>&1
 estatus=$?
 
 # Return the offset
-rm -f "${lock_path}.${OFFSET}.lock.d"
+rm -rf "${lock_path}.${OFFSET}.lock.d"
 
 if test $enable_hard_errors = no && test $estatus -eq 99; then
   tweaked_estatus=1