perf test: Checking BPF metadata collection fails on version string

perf test: Checking BPF metadata collection fails on version string

commit edf2cadf01e8f ("perf test: add test for BPF metadata collection")

fails consistently on the version string check. The perf version
string on some of the constant integration test machines contains
characters with special meaning in grep's extended regular expression
matching algorithm. The output of perf version is:

 # perf version
 perf version 6.17.0-20250814.rc1.git20.24ea63ea3877.63.fc42.s390x+git
 #

and the '+' character has special meaning in egrep command.
Also the use of egrep is deprecated.

Change the perf version string check to fixed character matching
and get rid of egrep's warning being deprecated. Use grep -F instead.

Output before:
 # perf test -F 102
 Checking BPF metadata collection
 egrep: warning: egrep is obsolescent; using grep -E
 Basic BPF metadata test [Failed invalid output]
 102: BPF metadata collection test             : FAILED!
 #

Output after:
 # perf test -F 102
 Checking BPF metadata collection
 Basic BPF metadata test [Success]
 102: BPF metadata collection test             : Ok
 #

Fixes: edf2cadf01e8f ("perf test: add test for BPF metadata collection")
Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Reviewed-by: Ian Rogers <irogers@google.com>
Reviewed-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Cc: Blake Jones <blakejones@google.com>
Link: https://lore.kernel.org/r/20250822122540.4104658-1-tmricht@linux.ibm.com
Signed-off-by: Namhyung Kim <namhyung@kernel.org>