pgsql: Minor kibitzing on previous patch: no need to run check more than

Log Message:
-----------
Minor kibitzing on previous patch: no need to run check more than once.
(_PG_init should be called only once anyway, but as long as it's got an
internal guard against repeat calls, that should be in front of the
version check.)

Modified Files:
--------------
    pgsql/src/pl/plpython:
        plpython.c (r1.147 -> r1.148)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/pl/plpython/plpython.c?r1=1.147&r2=1.148)