MySqlSshDriver.install fix: spilt yum installs

- On a CentOS 6.3 VM, the install of libgcc_s.so.1 failed with
  "Error: Protected multilib versions: libgcc-4.4.7-3.el6.i686 != libgcc-4.4.6-4.el6.x86_64".
  Therefore it didn't go on to next install of libaio.so.1 and 
  libncurses.so.5; easily fixed by splitting the install into two
  separate commands.