portageq get_repo_path: fix <eroot> parameter (bug 670082)

Use the @uses_configroot decorator to make portage get_repo_path
respect the <eroot> parameter, like portage repos_config since
commit 382f4be415394886026ccd5dcd08ca96ecda31fa.

Bug: https://bugs.gentoo.org/670082
Signed-off-by: Zac Medico <zmedico@gentoo.org>
diff --git a/bin/portageq b/bin/portageq
index c63591a..ab22b1c 100755
--- a/bin/portageq
+++ b/bin/portageq
@@ -882,6 +882,7 @@
 master_repos.__doc__ = docstrings['master_repos']
 
 
+@uses_configroot
 @uses_eroot
 def get_repo_path(argv):