MySQL table_open_cache size unusually small

https://bugzilla.redhat.com/show_bug.cgi?id=1080547
Users do not have the ability to change table_open_cache to values other
than 4 (and have them stick).  The set value seems too low to allow
database operations to remain efficient.  For example, in my app I have
18 tables that are constantly being written to from a single persistent
connection, but can only have four tables cached at a time.  This leads
to tables having to be re-opened which causes fairly significant disk
I/O.
Merge pull request #5063 from bparees/config_mysql_table_cache

Merged by openshift-bot