apache2: fix the race issue of parallel installation

fix following race issue when do parallel install
| mkdir: cannot create directory `/home/mypc/workspace/poky/build_p4080ds_release/tmp/work/ppce500mc-fsl_networking-linux/apache2/2.4.3-r1/image/usr/share/apache2': File exists
...
| mkdir: cannot create directory `/home/mypc/workspace/poky/build_p4080ds_release/tmp/work/ppce500mc-fsl_networking-linux/apache2/2.4.3-r1/image/usr/share/apache2': File exists
| make[1]: *** [install-man] Error 1
| make[1]: *** Waiting for unfinished jobs....

Signed-off-by: Zhenhua Luo <zhenhua.luo@freescale.com>