Fix(extra760): Error handling

[lazize]

Context

Missing permission was exposing AccessDenied error message.
Also missing check was generating false positive.

Description

Add check to validate access denied when get function from Lambda.

Issue #1014

License

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[lazize]

Please check additional questions on #1014

[lazize]

$ ./prowler -p default -f sa-east-1 -c extra760
                          _
  _ __  _ __ _____      _| | ___ _ __
 | '_ \| '__/ _ \ \ /\ / / |/ _ \ '__|
 | |_) | | | (_) \ V  V /| |  __/ |
 | .__/|_|  \___/ \_/\_/ |_|\___|_|v2.7.0-24January2022
 |_| the handy cloud security tool

 Date: Wed Feb  2 22:59:37 -03 2022

 Color code for results:
 -  INFO (Information)
 -  PASS (Recommended value)
 -  WARNING (Ignored by whitelist)
 -  FAIL (Fix required)

 This report is being generated using credentials below:

 AWS-CLI Profile: [default] AWS API Region: [sa-east-1] AWS Filter Region: [sa-east-1]
 AWS Account: [xxxx5262] UserId: [AROAxxxx:xxxxx]
 Caller Identity ARN: [arn:aws:sts::xxxx5262:assumed-role/xxxx/xxxxxx]

7.60 [extra760] Find secrets in Lambda functions code  - lambda [Critical]
       PASS! sa-east-1: No secrets found in Lambda function dump-request code
       PASS! sa-east-1: No secrets found in Lambda function test code

$ ./prowler -p default -f sa-east-1 -c extra760
                          _
  _ __  _ __ _____      _| | ___ _ __
 | '_ \| '__/ _ \ \ /\ / / |/ _ \ '__|
 | |_) | | | (_) \ V  V /| |  __/ |
 | .__/|_|  \___/ \_/\_/ |_|\___|_|v2.7.0-24January2022
 |_| the handy cloud security tool

 Date: Wed Feb  2 23:06:08 -03 2022

 Color code for results:
 -  INFO (Information)
 -  PASS (Recommended value)
 -  WARNING (Ignored by whitelist)
 -  FAIL (Fix required)

 This report is being generated using credentials below:

 AWS-CLI Profile: [default] AWS API Region: [sa-east-1] AWS Filter Region: [sa-east-1]
 AWS Account: [xxxx5262] UserId: [AROAxxxx:xxxxx]
 Caller Identity ARN: [arn:aws:sts::xxxx5262:assumed-role/xxxx/xxxxxx]

7.60 [extra760] Find secrets in Lambda functions code  - lambda [Critical]
       INFO! sa-east-1: Access Denied trying to get Lambda functions
       INFO! sa-east-1: Access Denied trying to get Lambda functions