service: propagate init error in EAL

service: propagate init error in EAL

Currently, when rte_service_init() fails at initialization, the
application always gets a ENOEXEC error code. For example, with testpmd,
this is displayed as:

  Cannot init EAL: Exec format error

This error code does not describe the real issue. Instead, use the error
code returned by the function.

Fixes: e39824500825 ("service: initialize with EAL")
Cc: stable@dpdk.org
Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
Acked-by: Harry van Haaren <harry.van.haaren@intel.com>