TT#59164 Field::URI allow "\\" char in sip-username

* \\ is allowed as it is used in the regexp match

Change-Id: I70619cb2ab44d40f1f7ecf15c1c37c20a8c232ea
(cherry picked from commit 7c22d44516)

lib/NGCP/Panel/Field/URI.pm

@@ -58,7 +58,7 @@ apply(
                 # "#" is from dtmf-digit => local-phone-number => telephone-subscriber 
                 # "%" is from escaped 
                 # ":" we will not separate username and password
-                my $userinfo_unreserved_chars = '&=+$,;?/#%:';
+                my $userinfo_unreserved_chars = '&=+$,;?/#%:\\';
 
                 my ($user, $domain) = split(/\@/, $value);