Prevent late initialization of GSS error map

Prevent late initialization of GSS error map

Some of the peripheral libgssapi_krb5 utility functions, such as
gss_str_to_oid(), do not access the mechanism list and therefore do
not reach any of the calls to gssint_mechglue_initialize_library().
If one of these functions is called early and produces an error, its
call to map_error() will operate on the uninitialized error map.  When
the library is later initialized, any entries added to the error map
this way will be leaked.

To ensure that the error map is initialized before it is operated on,
add library initialization calls to gssint_mecherrmap_map() and
gssint_mecherrmap_get().

ticket: 9145 (new)