pbx.c: Additional fixes to ast_context_remove_extension_callerid2.

Do not check registrar of the first extension head.  We should only check
the registrar when we match the priority.

Additionally fix a couple calls to strcmp which used the input callerid
instead of the clean version ex.cidmatch.

ASTERISK-26233

Change-Id: I17ea6881a18f40840ae9c1f5394aab1fbb3769f1