privvmpages 4052 49146 49152 53575 20
20 in last column means, that 20 times privvmpages barrier/limit was hitted. Thus 49152/53575 pages aren't enough for your situatation.
Just increase this limit:
vzctl set 1 --privvmpages 100000 --save
And retry to start apache. After that check /proc/user_beancounters to be sure, that 100000 pages are enough.
Good luck.