Fix testcase systemtap.unprivileged/unprivileged_embedded_C.exp

Fix testcase systemtap.unprivileged/unprivileged_embedded_C.exp

Commit 2f6fcfc6 (Fix BZ1546179 by being careful when accessing
sk_buff structures) made the "unprivileged_embedded_C.exp"
testcase unhappy.  It started to report false positives.

Thing is that embeddedc.awk can't correctly parse two block
boundaries at a line, which is exactly what the commit introduces
by adding "} catch { }", or "try { ... } catch { }".  Here is the
failure as observed with git stap 0e051c5:

=======
FAIL: unprivileged embedded C: : --unprivileged: Unterminated block at: function _input_route_type:long (skb:long): 2 0
FAIL: unprivileged embedded C: : --privilege=stapusr: Unterminated block at EOF: 2 0
FAIL: unprivileged embedded C: : --privilege=stapsys: Unterminated block at: function _input_route_type:long (skb:long): 2 0
FAIL: unprivileged embedded C: : --privilege=stapsys: Unterminated block at EOF: 2 0
FAIL: unprivileged embedded C (transitive): : --privilege=stapusr: Unterminated block at: function _input_route_type:long (skb:long): 2 0
FAIL: unprivileged embedded C (transitive): : --privilege=stapsys: Unterminated block at: function _input_route_type:long (skb:long): 2 0
=======

This commit tries to address the issue by making embeddedc.awk
able to process two block boundaries at a line.