git-p4: the option to specify 'host' is -H, not -h

This was broken since the feature was introduced initially at abcaf073 (If
the user has configured various parameters, use them., 2008-08-10).
Acked-by: NPete Wyckoff <pw@padd.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

contrib/fast-import/git-p4

@@ -38,7 +38,7 @@ def p4_build_cmd(cmd):
 
     host = gitConfig("git-p4.host")
     if len(host) > 0:
-        real_cmd += ["-h", host]
+        real_cmd += ["-H", host]
 
     client = gitConfig("git-p4.client")
     if len(client) > 0: