Correction of tracing from child process

Correction of tracing from child process
- There was read 16kb from pipe but only less then 1kb was traced.
  Rest of trace data was lost.
Added support for two EAL parameters:
  LogLevel - optional EAL paramenter which enable debug traces from rte libs
             If parameter is not used default trace level = 7 (INFO) is used
             LogLevel "8" - (DEBUG) can be set to collectd.conf into dpdkstat
             EAL section
  RteDriverLibPath - optional EAL parameter which enable loading of shared
                     pmd driver libs. Param value can be full path to single
                     pmd diriver lib or directory where pmd driver libs are
                     located. E.g.: "/usr/lib/dpdk-pmd/librte_pmd_i40e.so"
                                 or "/usr/lib/dpdk-pmd"

Signed-off-by: Jiri Prokes <jirix.x.prokes@intel.com>